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1
Jadhav, Pankaj Vilas, Vikrant Kumar Sinha, Saurabh Chugh, Chaithanya Kotyada, Digvijay Bachhav, Ramandeep Singh, Ulli Rothweiler, and Mahavir Singh. "2.09 Å Resolution structure of E. coli HigBA toxin–antitoxin complex reveals an ordered DNA-binding domain and intrinsic dynamics in antitoxin." Biochemical Journal 477, no. 20 (October 29, 2020): 4001–19. http://dx.doi.org/10.1042/bcj20200363.
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The toxin–antitoxin (TA) systems are small operon systems that are involved in important physiological processes in bacteria such as stress response and persister cell formation. Escherichia coli HigBA complex belongs to the type II TA systems and consists of a protein toxin called HigB and a protein antitoxin called HigA. The toxin HigB is a ribosome-dependent endoribonuclease that cleaves the translating mRNAs at the ribosome A site. The antitoxin HigA directly binds the toxin HigB, rendering the HigBA complex catalytically inactive. The existing biochemical and structural studies had revealed that the HigBA complex forms a heterotetrameric assembly via dimerization of HigA antitoxin. Here, we report a high-resolution crystal structure of E. coli HigBA complex that revealed a well-ordered DNA binding domain in HigA antitoxin. Using SEC-MALS and ITC methods, we have determined the stoichiometry of complex formation between HigBA and a 33 bp DNA and report that HigBA complex as well as HigA homodimer bind to the palindromic DNA sequence with nano molar affinity. Using E. coli growth assays, we have probed the roles of key, putative active site residues in HigB. Spectroscopic methods (CD and NMR) and molecular dynamics simulations study revealed intrinsic dynamic in antitoxin in HigBA complex, which may explain the large conformational changes in HigA homodimer in free and HigBA complexes observed previously. We also report a truncated, heterodimeric form of HigBA complex that revealed possible cleavage sites in HigBA complex, which can have implications for its cellular functions.
2
Norouzi, Masoumeh, Abbas Maleki, Elham Aboualigalehdari, and Sobhan Ghafourian. "Type II toxin- antitoxin systems in clinical isolates of antibiotic resistant Acinetobacter baumannii." Genetika 54, no. 2 (2022): 625–32. http://dx.doi.org/10.2298/gensr2202625n.
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The over use of antibiotics to treat infections in humans and animals made a phenomenon of the antibiotic-resistant bacteria. While studies focused to find on new antibiotics but, identification of novel antibacterial targets in bacteria is very important. By Toxin antitoxin systems this hypothesis could be done, whereas by the activation of a toxin or inactivation of an antitoxin, the raised toxin kills the bacterium. These systems are attractive target for antimicrobial therapy. However, the most important step for potency of TA system, as an antibacterial target, is to identify a TA system that is prevalent in all resistant clinical isolates. So, the prevalence of different TA systems among clinical isolates of Acinetobacter baumannii in Emam khomeini hospital, Ilam, Iran was evaluated to determine which TA system is prevalent in all antibiotic resistant A. baumannii. So, one hundred A. baumannii clinical isolates were identified during one-year period in Emam khomeini hospital, Ilam, Iran. A. baumannii clinical isolates were isolated from hospitalized patients in ICU and burn patients. All isolates were resistant to at least one antibiotic. Then, the isolates were subjected to evaluation to find mazEF and higBA TA genes by PCR. The results showed the frequency of mazEF and highBA TA genes in all isolates was 72% and 39%, respectively. mazEF or higBA TA systems are not presented in all isolates. So, the potency of these two TA systems are in challenged. Also, all isolates were not positive for one TA gene. So, more research in different geographical area should be done with functionality of TA genes.
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Park, Jin-Young, Hyo Jung Kim, Chinar Pathak, Hye-Jin Yoon, Do-Hee Kim, Sung Jean Park, and Bong-Jin Lee. "Induced DNA bending by unique dimerization of HigA antitoxin." IUCrJ 7, no. 4 (June 26, 2020): 748–60. http://dx.doi.org/10.1107/s2052252520006466.
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The bacterial toxin–antitoxin (TA) system regulates cell growth under various environmental stresses. Mycobacterium tuberculosis, the causative pathogen of tuberculosis (TB), has three HigBA type II TA systems with reverse gene organization, consisting of the toxin protein HigB and labile antitoxin protein HigA. Most type II TA modules are transcriptionally autoregulated by the antitoxin itself. In this report, we first present the crystal structure of the M. tuberculosis HigA3 antitoxin (MtHigA3) and MtHigA3 bound to its operator DNA complex. We also investigated the interaction between MtHigA3 and DNA using NMR spectroscopy. The MtHigA3 antitoxin structure is a homodimer that contains a structurally well conserved DNA-binding domain at the N-terminus and a dimerization domain at the C-terminus. Upon comparing the HigA homologue structures, a distinct difference was found in the C-terminal region that possesses the β-lid, and diverse orientations of two helix–turn–helix (HTH) motifs from HigA homologue dimers were observed. The structure of MtHigA3 bound to DNA reveals that the promoter DNA is bound to two HTH motifs of the MtHigA3 dimer presenting 46.5° bending, and the distance between the two HTH motifs of each MtHigA3 monomer was increased in MtHigA3 bound to DNA. The β-lid, which is found only in the tertiary structure of MtHigA3 among the HigA homologues, causes the formation of a tight dimerization network and leads to a unique arrangement for dimer formation that is related to the curvature of the bound DNA. This work could contribute to the understanding of the HigBA system of M. tuberculosis at the atomic level and may contribute to the development of new antibiotics for TB treatment.
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Klimkaitė, Laurita, Julija Armalytė, Jūratė Skerniškytė, and Edita Sužiedėlienė. "The Toxin-Antitoxin Systems of the Opportunistic Pathogen Stenotrophomonas maltophilia of Environmental and Clinical Origin." Toxins 12, no. 10 (October 1, 2020): 635. http://dx.doi.org/10.3390/toxins12100635.
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Stenotrophomonas maltophilia is a ubiquitous environmental bacterium that has recently emerged as a multidrug-resistant opportunistic pathogen causing bloodstream, respiratory, and urinary tract infections. The connection between the commensal environmental S. maltophilia and the opportunistic pathogen strains is still under investigation. Bacterial toxin–antitoxin (TA) systems have been previously associated with pathogenic traits, such as biofilm formation and resistance to antibiotics, which are important in clinical settings. The same species of the bacterium can possess various sets of TAs, possibly influencing their overall stress response. While the TA systems of other important opportunistic pathogens have been researched, nothing is known about the TA systems of S. maltophilia. Here, we report the identification and characterization of S. maltophilia type II TA systems and their prevalence in the isolates of clinical and environmental origins. We found 49 putative TA systems by bioinformatic analysis in S. maltophilia genomes. Despite their even spread in sequenced S. maltophilia genomes, we observed that relBE, hicAB, and previously undescribed COG3832-ArsR operons were present solely in clinical S. maltophilia isolates collected in Lithuania, while hipBA was more frequent in the environmental ones. The kill-rescue experiments in Escherichia coli proved higBA, hicAB, and relBE systems to be functional TA modules. Together with different TA profiles, the clinical S. maltophilia isolates exhibited stronger biofilm formation, increased antibiotic, and serum resistance compared to environmental isolates. Such tendencies suggest that certain TA systems could be used as indicators of virulence traits.
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Habib, Gul, Qing Zhu, and Baolin Sun. "Bioinformatics and Functional Assessment of Toxin-Antitoxin Systems in Staphylococcus aureus." Toxins 10, no. 11 (November 14, 2018): 473. http://dx.doi.org/10.3390/toxins10110473.
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Staphylococcus aureus is a nosocomial pathogen that can cause chronic to persistent infections. Among different mediators of pathogenesis, toxin-antitoxin (TA) systems are emerging as the most prominent. These systems are frequently studied in Escherichia coli and Mycobacterial species but rarely explored in S. aureus. In the present study, we thoroughly analyzed the S. aureus genome and screened all possible TA systems using the Rasta bacteria and toxin-antitoxin database. We further searched E. coli and Mycobacterial TA homologs and selected 67 TA loci as putative TA systems in S. aureus. The host inhibition of growth (HigBA) TA family was predominantly detected in S. aureus. In addition, we detected seven pathogenicity islands in the S. aureus genome that are enriched with virulence genes and contain 26 out of 67 TA systems. We ectopically expressed multiple TA genes in E. coli and S. aureus that exhibited bacteriostatic and bactericidal effects on cell growth. The type I Fst toxin created holes in the cell wall while the TxpA toxin reduced cell size and induced cell wall septation. Besides, we identified a new TA system whose antitoxin functions as a transcriptional autoregulator while the toxin functions as an inhibitor of autoregulation. Altogether, this study provides a plethora of new as well as previously known TA systems that will revitalize the research on S. aureus TA systems.
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Fivian-Hughes, Amanda S., and Elaine O. Davis. "Analyzing the Regulatory Role of the HigA Antitoxin within Mycobacterium tuberculosis." Journal of Bacteriology 192, no. 17 (June 28, 2010): 4348–56. http://dx.doi.org/10.1128/jb.00454-10.
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ABSTRACT Bacterial chromosomally encoded type II toxin-antitoxin (TA) loci may be involved in survival upon exposure to stress and have been linked to persistence and dormancy. Therefore, understanding the role of the numerous predicted TA loci within the human pathogen Mycobacterium tuberculosis has become a topic of great interest. Antitoxin proteins are known to autoregulate TA expression under normal growth conditions, but it is unknown whether they have a more global role in transcriptional regulation. This study focuses on analyzing the regulatory role of the M. tuberculosis HigA antitoxin. We first show that the M. tuberculosis higBA locus is functional within its native organism, as higB, higA, and Rv1957 were successfully deleted from the genome together while the deletion of higA alone was not possible. The effects of higB-Rv1957 deletion on M. tuberculosis global gene expression were investigated, and a number of potential HigA-regulated genes were identified. Transcriptional fusion and protein-DNA-binding assays were utilized to confirm the direct role of HigA in Rv1954A-Rv1957 repression, and the M. tuberculosis HigA DNA-binding motif was defined as ATATAGG(N6)CCTATAT. As HigA failed to bind to the next-most-closely related motif within the M. tuberculosis genome, HigA may not directly regulate any other genes in addition to its own operon.
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Kamruzzaman, Muhammad, Alma Y. Wu, and Jonathan R. Iredell. "Biological Functions of Type II Toxin-Antitoxin Systems in Bacteria." Microorganisms 9, no. 6 (June 11, 2021): 1276. http://dx.doi.org/10.3390/microorganisms9061276.
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After the first discovery in the 1980s in F-plasmids as a plasmid maintenance system, a myriad of toxin-antitoxin (TA) systems has been identified in bacterial chromosomes and mobile genetic elements (MGEs), including plasmids and bacteriophages. TA systems are small genetic modules that encode a toxin and its antidote and can be divided into seven types based on the nature of the antitoxin molecules and their mechanism of action to neutralise toxins. Among them, type II TA systems are widely distributed in chromosomes and plasmids and the best studied so far. Maintaining genetic material may be the major function of type II TA systems associated with MGEs, but the chromosomal TA systems contribute largely to functions associated with bacterial physiology, including the management of different stresses, virulence and pathogenesis. Due to growing interest in TA research, extensive work has been conducted in recent decades to better understand the physiological roles of these chromosomally encoded modules. However, there are still controversies about some of the functions associated with different TA systems. This review will discuss the most current findings and the bona fide functions of bacterial type II TA systems.
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Levante, Alessia, Camilla Lazzi, Giannis Vatsellas, Dimitris Chatzopoulos, Vasilis S. Dionellis, Periklis Makrythanasis, Erasmo Neviani, and Claudia Folli. "Genome Sequencing of five Lacticaseibacillus Strains and Analysis of Type I and II Toxin-Antitoxin System Distribution." Microorganisms 9, no. 3 (March 21, 2021): 648. http://dx.doi.org/10.3390/microorganisms9030648.
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The analysis of bacterial genomes is a potent tool to investigate the distribution of specific traits related to the ability of surviving in particular environments. Among the traits associated with the adaptation to hostile conditions, toxin–antitoxin (TA) systems have recently gained attention in lactic acid bacteria. In this work, genome sequences of Lacticaseibacillus strains of dairy origin were compared, focusing on the distribution of type I TA systems homologous to Lpt/RNAII and of the most common type II TA systems. A high number of TA systems have been identified spread in all the analyzed strains, with type I TA systems mainly located on plasmid DNA. The type II TA systems identified in these strains highlight the diversity of encoded toxins and antitoxins and their organization. This study opens future perspectives on the use of genomic data as a resource for the study of TA systems distribution and prevalence in microorganisms of industrial relevance.
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Kang, Sung-Min, Do-Hee Kim, Chenglong Jin, and Bong-Jin Lee. "A Systematic Overview of Type II and III Toxin-Antitoxin Systems with a Focus on Druggability." Toxins 10, no. 12 (December 4, 2018): 515. http://dx.doi.org/10.3390/toxins10120515.
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Toxin-antitoxin (TA) systems are known to play various roles in physiological processes, such as gene regulation, growth arrest and survival, in bacteria exposed to environmental stress. Type II TA systems comprise natural complexes consisting of protein toxins and antitoxins. Each toxin and antitoxin participates in distinct regulatory mechanisms depending on the type of TA system. Recently, peptides designed by mimicking the interfaces between TA complexes showed its potential to activate the activity of toxin by competing its binding counterparts. Type II TA systems occur more often in pathogenic bacteria than in their nonpathogenic kin. Therefore, they can be possible drug targets, because of their high abundance in some pathogenic bacteria, such as Mycobacterium tuberculosis. In addition, recent bioinformatic analyses have shown that type III TA systems are highly abundant in the intestinal microbiota, and recent clinical studies have shown that the intestinal microbiota is linked to inflammatory diseases, obesity and even several types of cancer. We therefore focused on exploring the putative relationship between intestinal microbiota-related human diseases and type III TA systems. In this paper, we review and discuss the development of possible druggable materials based on the mechanism of type II and type III TA system.
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Valizadeh, Nasrin, Firuzeh Valian, Nourkhoda Sadeghifard, Shahriar Karami, Iraj Pakzad, Hossein Kazemian, and Sobhan Ghafourian. "The Role of Peganum harmala Ethanolic Extract and Type II Toxin Antitoxin System in Biofilm Formation." Drug Research 67, no. 07 (March 20, 2017): 385–87. http://dx.doi.org/10.1055/s-0043-102060.
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AbstractToxin antitoxin system is a regulatory system that antitoxin inhibits the toxin. We aimed to determine the role of TA loci in biofilm formation in K. pneumoniae clinical and environmental isolates; also inhibition of biofilm formation by Peganum harmala. So, 40 K. pneumoniae clinical and environmental isolates were subjected for PCR to determine the frequency of mazEF, relEB, and mqsRA TA loci. Biofilm formation assay subjected for all isolates. Then, P. harmala was tested against positive biofilm formation strains. Our results demonstrated that relBE TA loci were dominant TA loci; whereas mqsRA TA loci were negative in all isolates. The most environmental isolates showed weak and no biofilm formation while strong and moderate biofilm formation observed in clinical isolates. Biofilm formations by K. pneumoniae in 9 ug/ml concentration were inhibited by P. harmala. In vivo study suggested to be performed to introduce Peganum harmala as anti-biofilm formation in K. pneumoniae.
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Lee, Ki-Young, and Bong-Jin Lee. "Dynamics-Based Regulatory Switches of Type II Antitoxins: Insights into New Antimicrobial Discovery." Antibiotics 12, no. 4 (March 23, 2023): 637. http://dx.doi.org/10.3390/antibiotics12040637.
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Type II toxin-antitoxin (TA) modules are prevalent in prokaryotes and are involved in cell maintenance and survival under harsh environmental conditions, including nutrient deficiency, antibiotic treatment, and human immune responses. Typically, the type II TA system consists of two protein components: a toxin that inhibits an essential cellular process and an antitoxin that neutralizes its toxicity. Antitoxins of type II TA modules typically contain the structured DNA-binding domain responsible for TA transcription repression and an intrinsically disordered region (IDR) at the C-terminus that directly binds to and neutralizes the toxin. Recently accumulated data have suggested that the antitoxin’s IDRs exhibit variable degrees of preexisting helical conformations that stabilize upon binding to the corresponding toxin or operator DNA and function as a central hub in regulatory protein interaction networks of the type II TA system. However, the biological and pathogenic functions of the antitoxin’s IDRs have not been well discussed compared with those of IDRs from the eukaryotic proteome. Here, we focus on the current state of knowledge about the versatile roles of IDRs of type II antitoxins in TA regulation and provide insights into the discovery of new antibiotic candidates that induce toxin activation/reactivation and cell death by modulating the regulatory dynamics or allostery of the antitoxin.
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Hosseini, Nava, Maryam Pourhajibagher, Nasim Chiniforush, Nazanin Hosseinkhan, Parizad Rezaie, and Abbas Bahador. "Modulation of Toxin-Antitoxin System Rnl AB Type II in Phage-Resistant Gammaproteobacteria Surviving Photodynamic Treatment." Journal of Lasers in Medical Sciences 10, no. 1 (December 15, 2018): 21–28. http://dx.doi.org/10.15171/jlms.2019.03.
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Type II toxin-antitoxin (TA) systems are the particular type of TA modules which take part in different kinds of cellular actions, such as biofilm formation, persistence, stress endurance, defense of the bacterial cell against multiple phage attacks, plasmid maintenance, and programmed cell death in favor of bacterial population. Although several bioinformatics and Pet lab studies have already been conducted to understand the functionality of already discovered TA systems, still, more work in this area is required. Rnl AB type II TA module, which is composed of RnlA toxin and RnlB antitoxin, is a newly discovered type II TA module which takes part in the defense mechanism against T4 bacteriophage attack in Escherichia coli K-12 strain MH1 that has not been widely studied in other bacteria. Because of the significant role of class Gammaproteobacteriacea in a diverse range of health problems, we chose here to focus on this class to survey the presence of the Rnl AB TA module. For better categorization and description of the distribution of this module in this class of bacteria, the corresponding phylogenetic trees are illustrated here. Neighbor-joining and the maximum parsimony methods were used in this study to take a look at the distribution of domains present in RnlA and RnlB proteins, among members of Gammaproteobacteria. Also, the possible roles of photodynamic therapy (PDT) in providing a substrate for better phage therapy are herein discussed.
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Alkhalili, Rawana, Joel Wallenius, and Björn Canbäck. "Towards Exploring Toxin-Antitoxin Systems in Geobacillus: A Screen for Type II Toxin-Antitoxin System Families in a Thermophilic Genus." International Journal of Molecular Sciences 20, no. 23 (November 22, 2019): 5869. http://dx.doi.org/10.3390/ijms20235869.
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The toxin-antitoxin (TA) systems have been attracting attention due to their role in regulating stress responses in prokaryotes and their biotechnological potential. Much recognition has been given to type II TA system of mesophiles, while thermophiles have received merely limited attention. Here, we are presenting the putative type II TA families encoded on the genomes of four Geobacillus strains. We employed the TA finder tool to mine for TA-coding genes and manually curated the results using protein domain analysis tools. We also used the NCBI BLAST, Operon Mapper, ProOpDB, and sequence alignment tools to reveal the geobacilli TA features. We identified 28 putative TA pairs, distributed over eight TA families. Among the identified TAs, 15 represent putative novel toxins and antitoxins, belonging to the MazEF, MNT-HEPN, ParDE, RelBE, and XRE-COG2856 TA families. We also identified a potentially new TA composite, AbrB-ParE. Furthermore, we are suggesting the Geobacillus acetyltransferase TA (GacTA) family, which potentially represents one of the unique TA families with a reverse gene order. Moreover, we are proposing a hypothesis on the xre-cog2856 gene expression regulation, which seems to involve the c-di-AMP. This study aims for highlighting the significance of studying TAs in Geobacillus and facilitating future experimental research.
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Tu, Chih-Han, Michelle Holt, Shengfeng Ruan, and Christina Bourne. "Evaluating the Potential for Cross-Interactions of Antitoxins in Type II TA Systems." Toxins 12, no. 6 (June 26, 2020): 422. http://dx.doi.org/10.3390/toxins12060422.
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The diversity of Type-II toxin–antitoxin (TA) systems in bacterial genomes requires tightly controlled interaction specificity to ensure protection of the cell, and potentially to limit cross-talk between toxin–antitoxin pairs of the same family of TA systems. Further, there is a redundant use of toxin folds for different cellular targets and complexation with different classes of antitoxins, increasing the apparent requirement for the insulation of interactions. The presence of Type II TA systems has remained enigmatic with respect to potential benefits imparted to the host cells. In some cases, they play clear roles in survival associated with unfavorable growth conditions. More generally, they can also serve as a “cure” against acquisition of highly similar TA systems such as those found on plasmids or invading genetic elements that frequently carry virulence and resistance genes. The latter model is predicated on the ability of these highly specific cognate antitoxin–toxin interactions to form cross-reactions between chromosomal antitoxins and invading toxins. This review summarizes advances in the Type II TA system models with an emphasis on antitoxin cross-reactivity, including with invading genetic elements and cases where toxin proteins share a common fold yet interact with different families of antitoxins.
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Hosseini, Mandana, Jamileh Nowroozi, and Nour Amirmozafari. "The effect of type II toxin-antitoxin systems on methicillinresistant Staphylococcus aureus persister cell formation and antibiotic tolerance." Acta Biologica Szegediensis 65, no. 1 (August 23, 2021): 113–17. http://dx.doi.org/10.14232/abs.2021.1.113-117.
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Persister cells are defi ned as a subpopulation of bacteria in a dormant state with the ability to reduce bacterial metabolism and they are involved in antibiotic tolerance. Toxin-antitoxin (TA) systems have been previously suggested as important players in persistence. Therefore, this study aimed to study the involvement of TA systems in persister cell formation in methicillin-resistant Staphylococcus aureus following antibiotic exposure. Using TADB and RASTA database, two type II TA systems including MazF/MazE and RelE/RelB were predicted in S. aureus. The presence of these TA genes was determined in 5 methicillin-resistant S. aureus isolates and the standard strain S. aureus subsp. aureus N315 using PCR method. To induce persistence, isolates were exposed to lethal doses of ciprofl oxacin and the expression of the studied TA system genes was measured after 5 h using Real-Time PCR. According to our results, all the studied isolates harbored the TA system genes. S. aureus was highly capable of persister cell formation following exposure to sub-MIC of ciprofl oxacin and RT-qPCR showed a signifi cant increase in the expression of the MazEF and RelBE loci, indicating their potential role in antibiotic tolerance. Considering the importance of antibiotic tolerance, further studies on persister cell formation and TA systems involved in this phenomenon are required to effi ciently target these systems.
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Xue, Lu, Jian Yue, Jiyuan Ke, Muhammad Hidayatullah Khan, Wen Wen, Baolin Sun, Zhongliang Zhu, and Liwen Niu. "Distinct oligomeric structures of the YoeB–YefM complex provide insights into the conditional cooperativity of type II toxin–antitoxin system." Nucleic Acids Research 48, no. 18 (August 26, 2020): 10527–41. http://dx.doi.org/10.1093/nar/gkaa706.
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Abstract YoeB–YefM, the widespread type II toxin–antitoxin (TA) module, binds to its own promoter to autoregulate its transcription: repress or induce transcription under normal or stress conditions, respectively. It remains unclear how YoeB–YefM regulates its transcription depending on the YoeB to YefM TA ratio. We find that YoeB–YefM complex from S.aureus exists as two distinct oligomeric assemblies: heterotetramer (YoeB–YefM2–YoeB) and heterohexamer (YoeB–YefM2–YefM2–YoeB) with low and high DNA-binding affinities, respectively. Structures of the heterotetramer alone and heterohexamer bound to promoter DNA reveals that YefM C-terminal domain undergoes disorder to order transition upon YoeB binding, which allosterically affects the conformation of N-terminal DNA-binding domain. At TA ratio of 1:2, unsaturated binding of YoeB to the C-terminal regions of YefM dimer forms an optimal heterohexamer for DNA binding, and two YefM dimers with N-terminal domains dock into the adjacent major grooves of DNA to specifically recognize the 5′-TTGTACAN6AGTACAA-3′ palindromic sequence, resulting in transcriptional repression. In contrast, at TA ratio of 1:1, binding of two additional YoeB molecules onto the heterohexamer induces the completely ordered conformation of YefM and disassembles the heterohexamer into two heterotetramers, which are unable to bind the promoter DNA optimally due to steric clashes, hence derepresses TA operon transcription.
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Gómez, Leonardo A., Raúl E. Molina, Rodrigo I. Soto, Manuel R. Flores, Roberto F. Coloma-Rivero, David A. Montero, and Ángel A. Oñate. "Unraveling the Role of the Zinc-Dependent Metalloproteinase/HTH-Xre Toxin/Antitoxin (TA) System of Brucella abortus in the Oxidative Stress Response: Insights into the Stress Response and Virulence." Toxins 15, no. 9 (August 31, 2023): 536. http://dx.doi.org/10.3390/toxins15090536.
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Toxin/antitoxin (TA) systems have been scarcely studied in Brucella abortus, the causative agent of brucellosis, which is one of the most prevalent zoonotic diseases worldwide. In this study, the roles of a putative type II TA system composed by a Zinc-dependent metalloproteinase (ZnMP) and a transcriptional regulator HTH-Xre were evaluated. The deletion of the open reading frame (ORF) BAB1_0270, coding for ZnMP, used to produce a mutant strain, allowed us to evaluate the survival and gene expression of B. abortus 2308 under oxidative conditions. Our results showed that the B. abortus mutant strain exhibited a significantly reduced capacity to survive under hydrogen peroxide-induced oxidative stress. Furthermore, this mutant strain showed a decreased expression of genes coding for catalase (katE), alkyl hydroperoxide reductase (ahpC) and transcriptional regulators (oxyR and oxyR-like), as well as genes involved in the general stress response, phyR and rpoE1, when compared to the wild-type strain. These findings suggest that this type II ZnMP/HTH-Xre TA system is required by B. abortus to resist oxidative stress. Additionally, previous evidence has demonstrated that this ZnMP also participates in the acidic stress resistance and virulence of B. abortus 2308. Therefore, we propose a hypothetical regulatory function for this ZnMP/HTH-Xre TA system, providing insight into the stress response and its potential roles in the pathogenesis of B. abortus.
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Ni, Songwei, Baiyuan Li, Kaihao Tang, Jianyun Yao, Thomas K. Wood, Pengxia Wang, and Xiaoxue Wang. "Conjugative plasmid-encoded toxin–antitoxin system PrpT/PrpA directly controls plasmid copy number." Proceedings of the National Academy of Sciences 118, no. 4 (January 22, 2021): e2011577118. http://dx.doi.org/10.1073/pnas.2011577118.
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Toxin–antitoxin (TA) loci were initially identified on conjugative plasmids, and one function of plasmid-encoded TA systems is to stabilize plasmids or increase plasmid competition via postsegregational killing. Here, we discovered that the type II TA system, Pseudoalteromonas rubra plasmid toxin–antitoxin PrpT/PrpA, on a low-copy-number conjugative plasmid, directly controls plasmid replication. Toxin PrpT resembles ParE of plasmid RK2 while antitoxin PrpA (PF03693) shares no similarity with previously characterized antitoxins. Surprisingly, deleting this prpA-prpT operon from the plasmid does not result in plasmid segregational loss, but greatly increases plasmid copy number. Mechanistically, the antitoxin PrpA functions as a negative regulator of plasmid replication, by binding to the iterons in the plasmid origin that inhibits the binding of the replication initiator to the iterons. We also demonstrated that PrpA is produced at a higher level than PrpT to prevent the plasmid from overreplicating, while partial or complete degradation of labile PrpA derepresses plasmid replication. Importantly, the PrpT/PrpA TA system is conserved and is widespread on many conjugative plasmids. Altogether, we discovered a function of a plasmid-encoded TA system that provides new insights into the physiological significance of TA systems.
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Zhou, Jingyi, Shouyi Li, Haozhou Li, Yongxin Jin, Fang Bai, Zhihui Cheng, and Weihui Wu. "Identification of a Toxin–Antitoxin System That Contributes to Persister Formation by Reducing NAD in Pseudomonas aeruginosa." Microorganisms 9, no. 4 (April 2, 2021): 753. http://dx.doi.org/10.3390/microorganisms9040753.
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Bacterial persisters are slow-growing or dormant cells that are highly tolerant to bactericidal antibiotics and contribute to recalcitrant and chronic infections. Toxin/antitoxin (TA) systems play important roles in controlling persister formation. Here, we examined the roles of seven predicted type II TA systems in the persister formation of a Pseudomonas aeruginosa wild-type strain PA14. Overexpression of a toxin gene PA14_51010 or deletion of the cognate antitoxin gene PA14_51020 increased the bacterial tolerance to antibiotics. Co-overexpression of PA14_51010 and PA14_51020 or simultaneous deletion of the two genes resulted in a wild-type level survival rate following antibiotic treatment. The two genes were located in the same operon that was repressed by PA14_51020. We further demonstrated the interaction between PA14_51010 and PA14_51020. Sequence analysis revealed that PA14_51010 contained a conserved RES domain. Overexpression of PA14_51010 reduced the intracellular level of nicotinamide adenine dinucleotide (NAD+). Mutation of the RES domain abolished the abilities of PA14_51010 in reducing NAD+ level and promoting persister formation. In addition, overproduction of NAD+ by mutation in an nrtR gene counteracted the effect of PA14_51010 overexpression in promoting persister formation. In combination, our results reveal a novel TA system that contributes to persister formation through reducing the intracellular NAD+ level in P. aeruginosa.
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Bajaj, R. Alexandra, Mark A. Arbing, Annie Shin, Duilio Cascio, and Linda Miallau. "Crystal structure of the toxin Msmeg_6760, the structural homolog ofMycobacterium tuberculosisRv2035, a novel type II toxin involved in the hypoxic response." Acta Crystallographica Section F Structural Biology Communications 72, no. 12 (November 19, 2016): 863–69. http://dx.doi.org/10.1107/s2053230x16017957.
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The structure of Msmeg_6760, a protein of unknown function, has been determined. Biochemical and bioinformatics analyses determined that Msmeg_6760 interacts with a protein encoded in the same operon, Msmeg_6762, and predicted that the operon is a toxin–antitoxin (TA) system. Structural comparison of Msmeg_6760 with proteins of known function suggests that Msmeg_6760 binds a hydrophobic ligand in a buried cavity lined by large hydrophobic residues. Access to this cavity could be controlled by a gate–latch mechanism. The function of the Msmeg_6760 toxin is unknown, but structure-based predictions revealed that Msmeg_6760 and Msmeg_6762 are homologous to Rv2034 and Rv2035, a predicted novel TA system involved inMycobacterium tuberculosislatency during macrophage infection. The Msmeg_6760 toxin fold has not been previously described for bacterial toxins and its unique structural features suggest that toxin activation is likely to be mediated by a novel mechanism.
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Tasneem, Maisha, Shipan Das Gupta, Monira Binte Momin, Kazi Modasser Hossain, Tasnim Binta Osman, and Md Fazley Rabbi. "In silico annotation of a hypothetical protein from Listeria monocytogenes EGD-e unfolds a toxin protein of the type II secretion system." Genomics & Informatics 21, no. 1 (March 31, 2023): e7. http://dx.doi.org/10.5808/gi.22071.
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The gram-positive bacterium Listeria monocytogenes is an important foodborne intracellular pathogen that is widespread in the environment. The functions of hypothetical proteins (HP) from various pathogenic bacteria have been successfully annotated using a variety of bioinformatics strategies. In this study, a HP Imo0888 (NP_464414.1) from the Listeria monocytogenes EGD-e strain was annotated using several bioinformatics tools. Various techniques, including CELLO, PSORTb, and SOSUIGramN, identified the candidate protein as cytoplasmic. Domain and motif analysis revealed that the target protein is a PemK/MazF-like toxin protein of the type II toxin-antitoxin system (TA) which was consistent with BLASTp analysis. Through secondary structure analysis, we found the random coil to be the most frequent. The Alpha Fold 2 Protein Structure Prediction Database was used to determine the three-dimensional (3D) structure of the HP using the template structure of a type II TA PemK/MazF family toxin protein (DB ID_AFDB: A0A4B9HQB9) with 99.1% sequence identity. Various quality evaluation tools, such as PROCHECK, ERRAT, Verify 3D, and QMEAN were used to validate the 3D structure. Following the YASARA energy minimization method, the target protein's 3D structure became more stable. The active site of the developed 3D structure was determined by the CASTp server. Most pathogens that harbor TA systems create a crucial risk to human health. Our aim to annotate the HP Imo088 found in Listeria could offer a chance to understand bacterial pathogenicity and identify a number of potential targets for drug development.
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Vogelgsang, Lars, Azlan Nisar, Sebastian Alexander Scharf, Anna Rommerskirchen, Dana Belick, Alexander Dilthey, and Birgit Henrich. "Characterisation of Type II DNA Methyltransferases of Metamycoplasma hominis." Microorganisms 11, no. 6 (June 15, 2023): 1591. http://dx.doi.org/10.3390/microorganisms11061591.
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Bacterial virulence, persistence and defence are affected by epigenetic modifications, including DNA methylation. Solitary DNA methyltransferases modulate a variety of cellular processes and influence bacterial virulence; as part of a restriction-modification (RM) system, they act as a primitive immune system in methylating the own DNA, while unmethylated foreign DNA is restricted. We identified a large family of type II DNA methyltransferases in Metamycoplasma hominis, comprising six solitary methyltransferases and four RM systems. Motif-specific 5mC and 6mA methylations were identified with a tailored Tombo analysis on Nanopore reads. Selected motifs with methylation scores >0.5 fit with the gene presence of DAM1 and DAM2, DCM2, DCM3, and DCM6, but not for DCM1, whose activity was strain-dependent. The activity of DCM1 for CmCWGG and of both DAM1 and DAM2 for GmATC was proven in methylation-sensitive restriction and finally for recombinant rDCM1 and rDAM2 against a dam-, dcm-negative background. A hitherto unknown dcm8/dam3 gene fusion containing a (TA) repeat region of varying length was characterized within a single strain, suggesting the expression of DCM8/DAM3 phase variants. The combination of genetic, bioinformatics, and enzymatic approaches enabled the detection of a huge family of type II DNA MTases in M. hominis, whose involvement in virulence and defence can now be characterized in future work.
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Heaton, Brook E., Julien Herrou, Anne E. Blackwell, Vicki H. Wysocki, and Sean Crosson. "Molecular Structure and Function of the Novel BrnT/BrnA Toxin-Antitoxin System of Brucella abortus." Journal of Biological Chemistry 287, no. 15 (February 14, 2012): 12098–110. http://dx.doi.org/10.1074/jbc.m111.332163.
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Type II toxin-antitoxin (TA) systems are expressed from two-gene operons that encode a cytoplasmic protein toxin and its cognate protein antitoxin. These gene cassettes are often present in multiple copies on bacterial chromosomes, where they have been reported to regulate stress adaptation and persistence during antimicrobial treatment. We have identified a novel type II TA cassette in the intracellular pathogen Brucella abortus that consists of the toxin gene, brnT, and its antitoxin, brnA. BrnT is coexpressed and forms a 2:2 tetrameric complex with BrnA, which neutralizes BrnT toxicity. The BrnT2-BrnA2 tetramer binds its own promoter via BrnA, and autorepresses its expression; its transcription is strongly induced in B. abortus by various stressors encountered by the bacterial cell during infection of a mammalian host. Although highly divergent at the primary sequence level, an atomic resolution (1.1 Å) crystal structure of BrnT reveals a secondary topology related to the RelE family of type II ribonuclease toxins. However, overall tertiary structural homology to other RelE family toxins is low. A functional characterization of BrnT by site-directed mutagenesis demonstrates a correspondence between its in vitro activity as a ribonuclease and control of bacteriostasis in vivo. We further present an analysis of the conserved and variable features of structure required for RNA scission in BrnT and the RelE toxin family. This structural investigation informs a model of the RelE-fold as an evolutionarily flexible scaffold that has been selected to bind structurally disparate antitoxins, and exhibit distinct toxin activities including RNA scission and DNA gyrase inhibition.
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Kędzierska, Barbara, and Katarzyna Potrykus. "Minigene as a Novel Regulatory Element in Toxin-Antitoxin Systems." International Journal of Molecular Sciences 22, no. 24 (December 13, 2021): 13389. http://dx.doi.org/10.3390/ijms222413389.
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The axe-txe type II toxin-antitoxin (TA) system is characterized by a complex and multilayered mode of gene expression regulation. Precise and tight control of this process is crucial to keep the toxin in an appropriate balance with the cognate antitoxin until its activation is needed for the cell. In this report, we provide evidence that a minigene encoded within the axe-txe operon influences translation of the Txe toxin. This is the first example to date of such a regulatory mechanism identified in the TA modules. Here, in a series of genetic studies, we employed translational reporter gene fusions to establish the molecular basis of this phenomenon. Our results show that translation of the two-codon mini-ORF displays an in cis mode of action, and positively affects the expression of txe, possibly by increasing its mRNA stability through protection from an endonuclease attack. Moreover, we established that the reading frame in which the two cistrons are encoded, as well as the distance between them, are critical parameters that affect the level of such regulation. In addition, by searching for two-codon ORFs we found sequences of several potential minigenes in the leader sequences of several other toxins belonging to the type II TA family. These findings suggest that this type of gene regulation may not only apply for the axe-txe cassette, but could be more widespread among other TA systems.
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Rathore, Jitendra Singh, and Lalit Kumar Gautam. "Expression, Purification, and Functional Analysis of Novel RelE Operon fromX. nematophila." Scientific World Journal 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/428159.
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Bacterial toxin-antitoxin (TA) complexes induce programmed cell death and also function to relieve cell from stress by various response mechanisms.Escherichia coliRelB-RelE TA complex consists of a RelE toxin functionally counteracted by RelB antitoxin. In the present study, a novel homolog of RelE toxin designated as Xn-relE toxin fromXenorhabdus nematophilapossessing its own antitoxin designated as Xn-relEAT has been identified. Expression and purification of recombinant proteins under native conditions with GST and Ni-NTA chromatography prove the existence of novel TA module. The expression of recombinant Xn-relE under tightly regulated ara promoter inE. coliTop 10 cells confirms its toxic nature in endogenous toxicity assay. The neutralization activity in endogenous toxicity assay by Xn-relEAT antitoxin confirms its antidote nature when studying the whole TA operon under ara regulated promoter. This study promotes newly discovered TA module to be regarded as important as other proteins of type II toxin-antitoxin system.
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Choi, Wonho, Yoshihiro Yamaguchi, Ji-Young Park, Sang-Hyun Park, Hyeok-Won Lee, Byung-Kwan Lim, Michael Otto, Masayori Inouye, Min-Ho Yoon, and Jung-Ho Park. "Functional Characterization of the mazEF Toxin-Antitoxin System in the Pathogenic Bacterium Agrobacterium tumefaciens." Microorganisms 9, no. 5 (May 20, 2021): 1107. http://dx.doi.org/10.3390/microorganisms9051107.
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Agrobacterium tumefaciens is a pathogen of various plants which transfers its own DNA (T-DNA) to the host plants. It is used for producing genetically modified plants with this ability. To control T-DNA transfer to the right place, toxin-antitoxin (TA) systems of A. tumefaciens were used to control the target site of transfer without any unintentional targeting. Here, we describe a toxin-antitoxin system, Atu0939 (mazE-at) and Atu0940 (mazF-at), in the chromosome of Agrobacterium tumefaciens. The toxin in the TA system has 33.3% identity and 45.5% similarity with MazF in Escherichia coli. The expression of MazF-at caused cell growth inhibition, while cells with MazF-at co-expressed with MazE-at grew normally. In vivo and in vitro assays revealed that MazF-at inhibited protein synthesis by decreasing the cellular mRNA stability. Moreover, the catalytic residue of MazF-at was determined to be the 24th glutamic acid using site-directed mutagenesis. From the results, we concluded that MazF-at is a type II toxin-antitoxin system and a ribosome-independent endoribonuclease. Here, we characterized a TA system in A. tumefaciens whose understanding might help to find its physiological function and to develop further applications.
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Jin, Chenglong, Sung-Min Kang, Do-Hee Kim, and Bong-Jin Lee. "Structural and functional analysis of the Klebsiella pneumoniae MazEF toxin–antitoxin system." IUCrJ 8, no. 3 (March 5, 2021): 362–71. http://dx.doi.org/10.1107/s2052252521000452.
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Bacterial toxin–antitoxin (TA) systems correlate strongly with physiological processes in bacteria, such as growth arrest, survival and apoptosis. Here, the first crystal structure of a type II TA complex structure of Klebsiella pneumoniae at 2.3 Å resolution is presented. The K. pneumoniae MazEF complex consists of two MazEs and four MazFs in a heterohexameric assembly. It was estimated that MazEF forms a dodecamer with two heterohexameric MazEF complexes in solution, and a truncated complex exists in heterohexameric form. The MazE antitoxin interacts with the MazF toxin via two binding modes, namely, hydrophobic and hydrophilic interactions. Compared with structural homologs, K. pneumoniae MazF shows distinct features in loops β1–β2, β3–β4 and β4–β5. It can be inferred that these three loops have the potential to represent the unique characteristics of MazF, especially various substrate recognition sites. In addition, K. pneumoniae MazF shows ribonuclease activity and the catalytic core of MazF lies in an RNA-binding pocket. Mutation experiments and cell-growth assays confirm Arg28 and Thr51 as critical residues for MazF ribonuclease activity. The findings shown here may contribute to the understanding of the bacterial MazEF TA system and the exploration of antimicrobial candidates to treat drug-resistant K. pneumoniae.
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Dong, Jinggang, Hanjie Gu, Huiqin Huang, Xiaoqian Tang, and Yonghua Hu. "Small RNA sR158 Participates in Oxidation Stress Tolerance and Pathogenicity of Edwardaiella piscicida by Regulating TA System YefM-YoeB." Aquaculture Research 2023 (May 16, 2023): 1–8. http://dx.doi.org/10.1155/2023/9967821.
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In recent years, the role of bacterial sRNAs in adversity tolerance and pathogens has attracted increasing attention. A great number of virulence-related sRNAs were reported in a variety of human pathogens. However, only a few sRNAs from aquatic pathogens were reported. In our previous study, a novel sRNA, sR158, was identified in Edwardsiella piscicida, an important aquatic pathogen, but its function remains unknown. In the same aquatic pathogen, we also identified a type II TA system, YefM-YoeB, in another study. In the current report, we found that the expression of yefM-yoeB in E. piscicida was regulated by sR158, which is dependent on the RNA chaperon Hfq. The deletion of sR158 reduced bacterial tolerance to oxidation pressure, enhanced bacterial capacity for biofilm formation, increased bacterial adhesion and invasion of host cells and immune tissues, and boosted bacterial general virulence, which are consistent with the effects caused by the deletion of YefM-YoeB. These findings indicate that sR158 participates in the stress resistance and virulence of E. piscicida by regulating YefM-YoeB. Our result is the first report that the type II TA system is regulated by sRNA, which provides new insights into the regulatory role of bacterial sRNA.
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Zhou, Juan, Xue-Jian Du, Ying Liu, Zeng-Qiang Gao, Zhi Geng, Yu-Hui Dong, and Heng Zhang. "Insights into the Neutralization and DNA Binding of Toxin–Antitoxin System ParESO-CopASO by Structure-Function Studies." Microorganisms 9, no. 12 (December 3, 2021): 2506. http://dx.doi.org/10.3390/microorganisms9122506.
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ParESO-CopASO is a new type II toxin–antitoxin (TA) system in prophage CP4So that plays an essential role in circular CP4So maintenance after the excision in Shewanella oneidensis. The toxin ParESO severely inhibits cell growth, while CopASO functions as an antitoxin to neutralize ParESO toxicity through direct interactions. However, the molecular mechanism of the neutralization and autoregulation of the TA operon transcription remains elusive. In this study, we determined the crystal structure of a ParESO-CopASO complex that adopted an open V-shaped heterotetramer with the organization of ParESO-(CopASO)2-ParESO. The structure showed that upon ParESO binding, the intrinsically disordered C-terminal domain of CopASO was induced to fold into a partially ordered conformation that bound into a positively charged and hydrophobic groove of ParESO. Thermodynamics analysis showed the DNA-binding affinity of CopASO was remarkably higher than that of the purified TA complex, accompanied by the enthalpy change reversion from an exothermic reaction to an endothermic reaction. These results suggested ParESO acts as a de-repressor of the TA operon transcription at the toxin:antitoxin level of 1:1. Site-directed mutagenesis of ParESO identified His91 as the essential residue for its toxicity by cell toxicity assays. Our structure-function studies therefore elucidated the transcriptional regulation mechanism of the ParESO-CopASO pair, and may help to understand the regulation of CP4So maintenance in S. oneidensis.
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Sofiev, M., R. Vankevich, M. Lanne, M. Prank, V. Petukhov, T. Ermakova, and J. Kukkonen. "An operational system for the assimilation of satellite information on wild-land fires for the needs of air quality modelling and forecasting." Atmospheric Chemistry and Physics Discussions 9, no. 2 (March 10, 2009): 6483–513. http://dx.doi.org/10.5194/acpd-9-6483-2009.
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Abstract. This paper investigates a potential of two remotely sensed wild-land fire characteristics: 4-μm Brightness Temperature Anomaly (TA) and Fire Radiative Power (FRP) for the needs of operational chemical transport modelling and the short-term forecasting of the atmospheric composition and air quality. Two treatments of the TA and FRP data are presented and a methodology for evaluating the emission fluxes is described. The method does not contain a complicated analysis of vegetation state, fuel load, burning efficiency and related factors, which are comparatively uncertain but inevitably involved in approaches based on burnt-area scars or similar products. The core of the current methodology is based on the empirical emission factors that have been derived from the analysis of several fire episodes in Europe (28 April–5 May 2006, 15–25 August 2006, August 2008 etc.). These episodes were characterised by: (i) well-identified FRP and TA values, and (ii) available independent observations of aerosol concentrations and optical thickness for the regions where fire smoke was dominant in comparison with contributions of other pollution sources. The emission factors were determined separately for the forested and grassland areas; in case of mixed-type land use an intermediate scaling was assumed. Despite significant difference between the TA and FRP products, an accurate non-linear fitting between the approaches was found. The agreement was comparatively weak only for small fires where the accuracy of both products is low. The re-analysis and forecasting applications of the Fire Assimilation System (FAS) showed that both TA and FRP products are suitable for evaluation of the emission fluxes from the wild-land fires. The concentrations of aerosols predicted by the regional dispersion modelling system SILAM appear within a factor of 2–3 from observations. The main areas of improvement include further refining the emission factors over the globe, explicit determination and appropriate treatment of the type of fires, evaluation of the injection height of the plumes and predicting the fire temporal evolution.
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Kang, Sung-Min, Ji Sung Koo, Chang-Min Kim, Do-Hee Kim, and Bong-Jin Lee. "mRNA Interferase Bacillus cereus BC0266 Shows MazF-Like Characteristics Through Structural and Functional Study." Toxins 12, no. 6 (June 8, 2020): 380. http://dx.doi.org/10.3390/toxins12060380.
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Toxin–antitoxin (TA) systems are prevalent in bacteria and are known to regulate cellular growth in response to stress. As various functions related to TA systems have been revealed, the importance of TA systems are rapidly emerging. Here, we present the crystal structure of putative mRNA interferase BC0266 and report it as a type II toxin MazF. The MazF toxin is a ribonuclease activated upon and during stressful conditions, in which it cleaves mRNA in a sequence-specific, ribosome-independent manner. Its prolonged activity causes toxic consequences to the bacteria which, in turn, may lead to bacterial death. In this study, we conducted structural and functional investigations of Bacillus cereus MazF and present the first toxin structure in the TA system of B. cereus. Specifically, B. cereus MazF adopts a PemK-like fold and also has an RNA substrate-recognizing loop, which is clearly observed in the high-resolution structure. Key residues of B. cereus MazF involved in the catalytic activity are also proposed, and in vitro assay together with mutational studies affirm the ribonucleic activity and the active sites essential for its cellular toxicity.
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Nishimura, Motoko, Shigeharu Uchida, Shigeki Mitsunaga, Yuji Yahagi, Kazunori Nakajima, Kenji Tadokoro, and Takeo Juji. "Characterization of T-Cell Clones Derived From Peripheral Blood Lymphocytes of a Patient With Transfusion-Associated Graft-Versus-Host Disease: Fas-Mediated Killing by CD4+ and CD8+ Cytotoxic T-Cell Clones and Tumor Necrosis Factor β Production by CD4+ T-Cell Clones." Blood 89, no. 4 (February 15, 1997): 1440–45. http://dx.doi.org/10.1182/blood.v89.4.1440.
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Abstract Transfusion-associated graft-versus-host disease (TA-GVHD) is one of the most serious adverse effects of blood transfusion. It is generally thought to be caused by the infused lymphocytes. Donor-derived cytotoxic T lymphocytes (CTLs) directed against the recipient's HLAs, which have escaped the recipient's immune system and are proliferating, are considered to attack recipient organs and tissues. Despite the seriousness of the disease, the precise mechanism of its development remains unclear and no definitive treatment has been developed. With the aim of developing an effective treatment, we established and characterized T-cell clones from peripheral blood lymphocytes (PBLs) of a TA-GVHD patient. Three types of clones were established. Type I clones were CD8+ and specifically lyse cells that express HLA B52. Type II clones were CD4+, specifically lysed cells that express HLA DR15, and proliferated in response to stimulation with cells that express DR15. Type III clones were also CD4+, showed no cytotoxic activity toward any HLA-expressing cells, and proliferated in response to stimulation with cells that express DR15. Furthermore, we found that the Fas/Fas-ligand (Fas-L) system is involved in the cytotoxicity of the type I and II clones and that the type III clones produce and secrete a large amount of tumor necrosis factor β (TNFβ) after antigen stimulation. Based on our results, these three types of clones can be classified into two categories: those that have the ability to induce GVHD directly by cytolysis and that show no cytotoxic activity and those that have the ability to cause GVHD indirectly through secretion of cytotoxic lymphokines.
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Bleriot, Ines, Lucia Blasco, Mercedes Delgado-Valverde, Ana Gual-de-Torrella, Anton Ambroa, Laura Fernandez-Garcia, Maria Lopez, et al. "Mechanisms of Tolerance and Resistance to Chlorhexidine in Clinical Strains of Klebsiella pneumoniae Producers of Carbapenemase: Role of New Type II Toxin-Antitoxin System, PemIK." Toxins 12, no. 9 (September 2, 2020): 566. http://dx.doi.org/10.3390/toxins12090566.
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Although the failure of antibiotic treatment is normally attributed to resistance, tolerance and persistence display a significant role in the lack of response to antibiotics. Due to the fact that several nosocomial pathogens show a high level of tolerance and/or resistance to chlorhexidine, in this study we analyzed the molecular mechanisms associated with chlorhexidine adaptation in two clinical strains of Klebsiella pneumoniae by phenotypic and transcriptomic studies. These two strains belong to ST258-KPC3 (high-risk clone carrying β-lactamase KPC3) and ST846-OXA48 (low-risk clone carrying β-lactamase OXA48). Our results showed that the K. pneumoniae ST258-KPC3CA and ST846-OXA48CA strains exhibited a different behavior under chlorhexidine (CHLX) pressure, adapting to this biocide through resistance and tolerance mechanisms, respectively. Furthermore, the appearance of cross-resistance to colistin was observed in the ST846-OXA48CA strain (tolerant to CHLX), using the broth microdilution method. Interestingly, this ST846-OXA48CA isolate contained a plasmid that encodes a novel type II toxin/antitoxin (TA) system, PemI/PemK. We characterized this PemI/PemK TA system by cloning both genes into the IPTG-inducible pCA24N plasmid, and found their role in persistence and biofilm formation. Accordingly, the ST846-OXA48CA strain showed a persistence biphasic curve in the presence of a chlorhexidine-imipenem combination, and these results were confirmed by the enzymatic assay (WST-1).
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Lyman, M. G., C. D. Kemp, M. P. Taylor, and L. W. Enquist. "Comparison of the Pseudorabies Virus Us9 Protein with Homologs from Other Veterinary and Human Alphaherpesviruses." Journal of Virology 83, no. 14 (May 6, 2009): 6978–86. http://dx.doi.org/10.1128/jvi.00598-09.
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ABSTRACT Pseudorabies virus (PRV) Us9 is a small, tail-anchored (TA) membrane protein that is essential for axonal sorting of viral structural proteins and is highly conserved among other members of the alphaherpesvirus subfamily. We cloned the Us9 homologs from two human pathogens, varicella-zoster virus (VZV) and herpes simplex virus type 1 (HSV-1), as well as two veterinary pathogens, equine herpesvirus type 1 (EHV-1) and bovine herpesvirus type 1 (BHV-1), and fused them to enhanced green fluorescent protein to examine their subcellular localization and membrane topology. Akin to PRV Us9, all of the Us9 homologs localized to the trans-Golgi network and had a type II membrane topology (typical of TA proteins). Furthermore, we examined whether any of the Us9 homologs could compensate for the loss of PRV Us9 in anterograde, neuron-to-cell spread of infection in a compartmented chamber system. EHV-1 and BHV-1 Us9 were able to fully compensate for the loss of PRV Us9, whereas VZV and HSV-1 Us9 proteins were unable to functionally replace PRV Us9 when they were expressed in a PRV background.
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Maggi, Stefano, Alberto Ferrari, Korotoum Yabre, Aleksandra Anna Bonini, Claudio Rivetti, and Claudia Folli. "Strategies to Investigate Membrane Damage, Nucleoid Condensation, and RNase Activity of Bacterial Toxin–Antitoxin Systems." Methods and Protocols 4, no. 4 (October 8, 2021): 71. http://dx.doi.org/10.3390/mps4040071.
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A large number of bacterial toxin–antitoxin (TA) systems have been identified so far and different experimental approaches have been explored to investigate their activity and regulation both in vivo and in vitro. Nonetheless, a common feature of these methods is represented by the difficulty in cell transformation, culturing, and stability of the transformants, due to the expression of highly toxic proteins. Recently, in dealing with the type I Lpt/RNAII and the type II YafQ/DinJ TA systems, we encountered several of these problems that urged us to optimize methodological strategies to study the phenotype of recombinant Escherichia coli host cells. In particular, we have found conditions to tightly repress toxin expression by combining the pET expression system with the E. coli C41(DE3) pLysS strain. To monitor the RNase activity of the YafQ toxin, we developed a fluorescence approach based on Thioflavin-T which fluoresces brightly when complexed with bacterial RNA. Fluorescence microscopy was also applied to reveal loss of membrane integrity associated with the activity of the type I toxin Lpt, by using DAPI and ethidium bromide to selectively stain cells with impaired membrane permeability. We further found that atomic force microscopy can readily be employed to characterize toxin-induced membrane damages.
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Ariyachaokun, Kanchiyaphat, Anna D. Grabowska, Claude Gutierrez, and Olivier Neyrolles. "Multi-Stress Induction of the Mycobacterium tuberculosis MbcTA Bactericidal Toxin-Antitoxin System." Toxins 12, no. 5 (May 16, 2020): 329. http://dx.doi.org/10.3390/toxins12050329.
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MbcTA is a type II toxin/antitoxin (TA) system of Mycobacterium tuberculosis. The MbcT toxin triggers mycobacterial cell death in vitro and in vivo through the phosphorolysis of the essential metabolite NAD+ and its bactericidal activity is neutralized by physical interaction with its cognate antitoxin MbcA. Therefore, the MbcTA system appears as a promising target for the development of novel therapies against tuberculosis, through the identification of compounds able to antagonize or destabilize the MbcA antitoxin. Here, the expression of the mbcAT operon and its regulation were investigated. A dual fluorescent reporter system was developed, based on an integrative mycobacterial plasmid that encodes a constitutively expressed reporter, serving as an internal standard for monitoring mycobacterial gene expression, and an additional reporter, dependent on the promoter under investigation. This system was used both in M. tuberculosis and in the fast growing model species Mycobacterium smegmatis to: (i) assess the autoregulation of mbcAT; (ii) perform a genetic dissection of the mbcA promoter/operator region; and (iii) explore the regulation of mbcAT transcription from the mbcA promoter (PmbcA) in a variety of stress conditions, including in vivo in mice and in macrophages.
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Jurėnas, Dukas, Laurence Van Melderen, and Abel Garcia-Pino. "Crystallization and X-ray analysis of all of the players in the autoregulation of theataRTtoxin–antitoxin system." Acta Crystallographica Section F Structural Biology Communications 74, no. 7 (June 26, 2018): 391–401. http://dx.doi.org/10.1107/s2053230x18007914.
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TheataRToperon from enteropathogenicEscherichia coliencodes a toxin–antitoxin (TA) module with a recently discovered novel toxin activity. This new type II TA module targets translation initiation for cell-growth arrest. Virtually nothing is known regarding the molecular mechanisms of neutralization, toxin catalytic action or translation autoregulation. Here, the production, biochemical analysis and crystallization of the intrinsically disordered antitoxin AtaR, the toxin AtaT, the AtaR–AtaT complex and the complex of AtaR–AtaT with a double-stranded DNA fragment of the operator region of the promoter are reported. Because they contain large regions that are intrinsically disordered, TA antitoxins are notoriously difficult to crystallize. AtaR forms a homodimer in solution and crystallizes in space groupP6122, with unit-cell parametersa = b = 56.3,c= 160.8 Å. The crystals are likely to contain an AtaR monomer in the asymmetric unit and diffracted to 3.8 Å resolution. The Y144F catalytic mutant of AtaT (AtaTY144F) bound to the cofactor acetyl coenzyme A (AcCoA) and the C-terminal neutralization domain of AtaR (AtaR44–86) were also crystallized. The crystals of the AtaTY144F–AcCoA complex diffracted to 2.5 Å resolution and the crystals of AtaR44–86diffracted to 2.2 Å resolution. Analysis of these structures should reveal the full scope of the neutralization of the toxin AtaT by AtaR. The crystals belonged to space groupsP6522 andP3121, with unit-cell parametersa=b= 58.1,c= 216.7 Å anda=b= 87.6,c = 125.5 Å, respectively. The AtaR–AtaT–DNA complex contains a 22 bp DNA duplex that was optimized to obtain high-resolution data based on the sequence of two inverted repeats detected in the operator region. It crystallizes in space groupC2221, with unit-cell parametersa= 75.6,b= 87.9,c= 190.5 Å. These crystals diffracted to 3.5 Å resolution.
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Kim, Do-Hee, Sung-Min Kang, Sung-Min Baek, Hye-Jin Yoon, Dong Man Jang, Hyoun Sook Kim, Sang Jae Lee, and Bong-Jin Lee. "Role of PemI in the Staphylococcus aureus PemIK toxin–antitoxin complex: PemI controls PemK by acting as a PemK loop mimic." Nucleic Acids Research 50, no. 4 (February 10, 2022): 2319–33. http://dx.doi.org/10.1093/nar/gkab1288.
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Abstract Staphylococcus aureus is a notorious and globally distributed pathogenic bacterium. New strategies to develop novel antibiotics based on intrinsic bacterial toxin–antitoxin (TA) systems have been recently reported. Because TA systems are present only in bacteria and not in humans, these distinctive systems are attractive targets for developing antibiotics with new modes of action. S. aureus PemIK is a type II TA system, comprising the toxin protein PemK and the labile antitoxin protein PemI. Here, we determined the crystal structures of both PemK and the PemIK complex, in which PemK is neutralized by PemI. Our biochemical approaches, including fluorescence quenching and polarization assays, identified Glu20, Arg25, Thr48, Thr49, and Arg84 of PemK as being important for RNase function. Our study indicates that the active site and RNA-binding residues of PemK are covered by PemI, leading to unique conformational changes in PemK accompanied by repositioning of the loop between β1 and β2. These changes can interfere with RNA binding by PemK. Overall, PemK adopts particular open and closed forms for precise neutralization by PemI. This structural and functional information on PemIK will contribute to the discovery and development of novel antibiotics in the form of peptides or small molecules inhibiting direct binding between PemI and PemK.
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amraei, Fatemeh, Negar narimisa, Behrooz sadeghi kalani, Rokhsareh mohammadzadeh, Vahid lohrasbi, and Faramarz masjedian jazi. "The expression of type II TA system genes following exposure to the sub-inhibitory concentration of gentamicin and acid stress in Brucella spp." Microbial Pathogenesis 144 (July 2020): 104194. http://dx.doi.org/10.1016/j.micpath.2020.104194.
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Song, Cheng, Mingyue Zhang, Zongpu Jia, Weiping Peng, and Hairu Guo. "A lightweight batch anonymous authentication scheme for VANET based on pairing-free." Computer Science and Information Systems 15, no. 3 (2018): 549–67. http://dx.doi.org/10.2298/csis171222022s.
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Aimed at improving the security and efficiency of anonymous authentication in vehicular ad hoc network (VANET), a certificateless batch anonymous authentication scheme without bilinear pairings is put forward. By coordinating Trust Authority (TA) and vehicles to generate the public/private key pairs and pseudonyms, the system security is freed from dependency on tamperproof devices. Through comprehensive analyses, this scheme is proved not only to be able to realize such security properties as authentication, anonymity, traceability, unforgeability, forward or backward security, etc., but also able to resist Type I and Type II attacks in the random oracle model. Moreover, this scheme effectively reduces system storage load by means of certificateless authentication, and the authentication efficiency can also be increased by realizing batch authentication based on pairing-free calculation. Accordingly, the scheme is proved to be significant in theory and valuable in application in the Internet of Things or embedded environment with limited resources.
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Asseck, Lisa Yasmin, Dietmar Gerald Mehlhorn, Jhon Rivera Monroy, Martiniano Maria Ricardi, Holger Breuninger, Niklas Wallmeroth, Kenneth Wayne Berendzen, et al. "Endoplasmic reticulum membrane receptors of the GET pathway are conserved throughout eukaryotes." Proceedings of the National Academy of Sciences 118, no. 1 (December 21, 2020): e2017636118. http://dx.doi.org/10.1073/pnas.2017636118.
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Type II tail-anchored (TA) membrane proteins are involved in diverse cellular processes, including protein translocation, vesicle trafficking, and apoptosis. They are characterized by a single C-terminal transmembrane domain that mediates posttranslational targeting and insertion into the endoplasmic reticulum (ER) via the Guided-Entry of TA proteins (GET) pathway. The GET system was originally described in mammals and yeast but was recently shown to be partially conserved in other eukaryotes, such as higher plants. A newly synthesized TA protein is shielded from the cytosol by a pretargeting complex and an ATPase that delivers the protein to the ER, where membrane receptors (Get1/WRB and Get2/CAML) facilitate insertion. In the model plantArabidopsis thaliana, most components of the pathway were identified throughin silicosequence comparison, however, a functional homolog of the coreceptor Get2/CAML remained elusive. We performed immunoprecipitation-mass spectrometry analysis to detect in vivo interactors ofAtGET1 and identified a membrane protein of unknown function with low sequence homology but high structural homology to both yeast Get2 and mammalian CAML. The protein localizes to the ER membrane, coexpresses withAtGET1, and binds toArabidopsisGET pathway components. While loss-of-function lines phenocopy the stunted root hair phenotype of otherAtgetlines, its heterologous expression together with the coreceptorAtGET1 rescues growth defects ofΔget1get2yeast. Ectopic expression of the cytosolic, positively charged N terminus is sufficient to block TA protein insertion in vitro. Our results collectively confirm that we have identified a plant-specific GET2 inArabidopsis, and its sequence allows the analysis of cross-kingdom pathway conservation.
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Sofiev, M., R. Vankevich, M. Lotjonen, M. Prank, V. Petukhov, T. Ermakova, J. Koskinen, and J. Kukkonen. "An operational system for the assimilation of the satellite information on wild-land fires for the needs of air quality modelling and forecasting." Atmospheric Chemistry and Physics 9, no. 18 (September 18, 2009): 6833–47. http://dx.doi.org/10.5194/acp-9-6833-2009.
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Abstract. This paper investigates a potential of two remotely sensed wild-land fire characteristics: 4-μm Brightness Temperature Anomaly (TA) and Fire Radiative Power (FRP) for the needs of operational chemical transport modelling and short-term forecasting of atmospheric composition and air quality. The treatments of the TA and FRP data are presented and a methodology for evaluating the emission fluxes of primary aerosols (PM2.5 and total PM) is described. The method does not include the complicated analysis of vegetation state, fuel load, burning efficiency and related factors, which are uncertain but inevitably involved in approaches based on burnt-area scars or similar products. The core of the current methodology is based on the empirical emission factors that are used to convert the observed temperature anomalies and fire radiative powers into emission fluxes. These factors have been derived from the analysis of several fire episodes in Europe (28.4–5.5.2006, 15.8–25.8.2006 and in August 2008). These episodes were characterised by: (i) well-identified FRP and TA values, and (ii) available ground-based observations of aerosol concentrations, and optical thickness for the regions where the contribution of the fire smoke to the concentrations of PM2.5 was dominant, in comparison with those of other pollution sources. The emission factors were determined separately for the forested and grassland areas; in case of mixed-type land use, an intermediate scaling was assumed. Despite significant differences between the TA and FRP methodologies, an accurate non-linear fitting was found between the predictions of these approaches. The agreement was comparatively weak only for small fires, for which the accuracy of both products is expected to be low. The applications of the Fire Assimilation System (FAS) in combination with the dispersion model SILAM showed that both the TA and FRP products are suitable for the evaluation of the emission fluxes from wild-land fires. The fire-originated concentrations of aerosols (PM2.5, PM10, sulphates and nitrates) and AOD, as predicted by the SILAM model were mainly within a factor of 2–3 compared with the observations. The main challenges of the FAS improvement include refining of the emission factors globally, determination of the types of fires (smouldering vs flaming), evaluation of the injection heights of the plumes, and predicting the temporal evolution of fires.
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Wen, Wen, Banghui Liu, Lu Xue, Zhongliang Zhu, Liwen Niu, and Baolin Sun. "Autoregulation and Virulence Control by the Toxin-Antitoxin System SavRS inStaphylococcus aureus." Infection and Immunity 86, no. 5 (February 12, 2018): e00032-18. http://dx.doi.org/10.1128/iai.00032-18.
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ABSTRACTToxin-antitoxin (TA) systems play diverse physiological roles, such as plasmid maintenance, growth control, and persister cell formation, but their involvement in bacterial pathogenicity remains largely unknown. Here, we have identified a novel type II toxin-antitoxin system, SavRS, and revealed the molecular mechanisms of its autoregulation and virulence control inStaphylococcus aureus. Electrophoretic mobility shift assay and isothermal titration calorimetry data indicated that the antitoxin SavR acted as the primary repressor bound to its own promoter, while the toxin SavS formed a complex with SavR to enhance the ability to bind to the operator site. DNase I footprinting assay identified the SavRS-binding site containing a short and long palindrome in the promoter region. Further, mutation and DNase I footprinting assay demonstrated that the two palindromes were crucial for DNA binding and transcriptional repression. More interestingly, genetic deletion of thesavRSsystem led to the increased hemolytic activity and pathogenicity in a mouse subcutaneous abscess model. We further identified two virulence genes,hlaandefb, by real-time quantitative reverse transcription-PCR and demonstrated that SavR and SavRS could directly bind to their promoter regions to repress virulence gene expression.
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Ninkovic, Vladan, Srdjan Ninkovic, and Dragana Zivojinovic. "Cardiovascular autonomous dysfunction in diabetics: The influence of disease duration, glycoregulation degree and diabetes type." Srpski arhiv za celokupno lekarstvo 136, no. 9-10 (2008): 488–93. http://dx.doi.org/10.2298/sarh0810488n.
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INTRODUCTION Cardiovascular autonomous neuropathy (CAN) in diabetes has not been still defined clinically and aetiopathogenetically. OBJECTIVE The aim of this study was to determine the influence of disease duration, glycoregulation degree and diabetes type on damage of the cardiovascular part of the autonomous nervous system in our group of patients. METHOD This study included diabetics, (100 patients) the same number of patients with diabetes type I and II as well as 20 healthy individuals in the control group. Classic Ewing's cardiovascular tests were used for CAN diagnosis: 1. the cardiovascular response to Valsalva manoeuvre, 2. the cardiovascular response to deep breathing (the so-called E/I ratio), 3. the cardiovascular response to rising (the so-called 30/15 ratio), 4. the test of orthostatic hypotension and 5. the TA response to handgrip. It has been arbitrarily taken that patients, whose score of 'parasympathetic' tests (Valsalva manoeuvre, E/I ratio, 30/15) is equal or bigger than 1.5 (out of possible 3), have damage of the parasympathetic part of the autonomous nervous system while patients, whose score of 'sympathetic tests' (the test of orthostatic hypotension and TA response to hand-grip is equal or bigger than 1 (out of possible 2), have damage of the sympathetic part of the autonomous nervous system. The patients whose total score is equal or bigger than 2 have cardiovascular autonomous neuropathy. The glycoregulation degree is determined by the level of HbA1c. RESULTS There is a statistically significant, positive correlation between the values of the parasympathetic score and disease duration as well as between the total score, that is, CAN and disease duration. The connection between the sympathetic score, that is, damage of the sympathetic part of the autonomous nervous system and disease duration has not been observed. There is a positive correlation between the values of the parasympathetic score and HbA1c. The same pattern exists regarding the ratio of damage of the sympathetic part of the autonomous nervous system and the value of HbA1c, as well as the ratio of CAN, that is, the total score and HbA1c. Almost two- fold, a bigger coefficient of correlation between the sympathetic score and HbA1c in relation to the coefficient of correlation of the parasympathetic score and HbA1c, points to bigger sensitivity of the sympathetic part of the autonomous nervous system to subacute deterioration of glycoregulation. The correlation between the values of autonomous scores and diabetes type has not been noted. CONCLUSION Our results show that besides disease duration, the subacute deterioration of glycoregulation also leads to the appearance of cardiovascular autonomous dysfunction in diabetes. The sympathetic nervous tissue is functionally more sensitive than the parasympathetic one to metabolic disorders in diabetes. The cardiovascular autonomous dysfunction will occur independently of the type of diabetes.
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Tamman, Hedvig, Andres Ainelo, Mari Tagel, and Rita Hõrak. "Stability of the GraA Antitoxin Depends on Growth Phase, ATP Level, and Global Regulator MexT." Journal of Bacteriology 198, no. 5 (December 14, 2015): 787–96. http://dx.doi.org/10.1128/jb.00684-15.
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ABSTRACTBacterial type II toxin-antitoxin systems consist of a potentially poisonous toxin and an antitoxin that inactivates the toxic protein by binding to it. Most of the toxins regulate stress survival, but their activation depends on the stability of the antitoxin that has to be degraded in order for the toxin to be able to attack its cellular targets. The degradation of antitoxins is usually rapid and carried out by ATP-dependent protease Lon or Clp, which is activated under stress conditions. ThegraTAsystem ofPseudomonas putidaencodes the toxin GraT, which can affect the growth rate and stress tolerance of bacteria but is under most conditions inactivated by the unusually stable antitoxin GraA. Here, we aimed to describe the stability features of the antitoxin GraA by analyzing its degradation rate in total cell lysates ofP. putida. We show that the degradation rate of GraA depends on the growth phase of bacteria being fastest in the transition from exponential to stationary phase. In accordance with this, higher ATP levels were shown to stabilize GraA. Differently from other antitoxins, the main cellular proteases Lon and Clp are not involved in GraA stability. Instead, GraA seems to be degraded through a unique pathway involving an endoprotease that cleaves the antitoxin into two unequal parts. We also identified the global transcriptional regulator MexT as a factor for destabilization of GraA, which indicates that the degradation of GraA may be induced by conditions similar to those that activate MexT.IMPORTANCEToxin-antitoxin (TA) modules are widespread in bacterial chromosomes and have important roles in stress tolerance. As activation of a type II toxin is triggered by proteolytic degradation of the antitoxin, knowledge about the regulation of the antitoxin stability is critical for understanding the activation of a particular TA module. Here, we report on the unusual degradation pathway of the antitoxin GraA of the recently characterized GraTA system. While GraA is uncommonly stable in the exponential and late-stationary phases, its degradation increases in the transition phase. The degradation pathway of GraA involves neither Lon nor Clp, which usually targets antitoxins, but rather an unknown endoprotease and the global regulator MexT, suggesting a new type of regulation of antitoxin stability.
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Moreno-Córdoba, Inmaculada, Wai-Ting Chan, Concha Nieto, and Manuel Espinosa. "Interactions of the Streptococcus pneumoniae Toxin-Antitoxin RelBE Proteins with Their Target DNA." Microorganisms 9, no. 4 (April 15, 2021): 851. http://dx.doi.org/10.3390/microorganisms9040851.
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Type II bacterial toxin-antitoxin (TA) systems are found in most bacteria, archaea, and mobile genetic elements. TAs are usually found as a bi-cistronic operon composed of an unstable antitoxin and a stable toxin that targets crucial cellular functions like DNA supercoiling, cell-wall synthesis or mRNA translation. The type II RelBE system encoded by the pathogen Streptococcus pneumoniae is highly conserved among different strains and participates in biofilm formation and response to oxidative stress. Here, we have analyzed the participation of the RelB antitoxin and the RelB:RelE protein complex in the self-regulation of the pneumococcal relBE operon. RelB acted as a weak repressor, whereas RelE performed the role of a co-repressor. By DNA footprinting experiments, we show that the proteins bind to a region that encompasses two palindromic sequences that are located around the −10 sequences of the single promoter that directs the synthesis of the relBE mRNA. High-resolution footprinting assays showed the distribution of bases whose deoxyriboses are protected by the bound proteins, demonstrating that RelB and RelB:RelE contacted the DNA backbone on one face of the DNA helix and that these interactions extended beyond the palindromic sequences. Our findings suggest that the binding of the RelBE proteins to its DNA target would lead to direct inhibition of the binding of the host RNA polymerase to the relBE promoter.
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Ovčačíková, Hana, Marek Velička, Jozef Vlček, Michaela Topinková, Miroslava Klárová, and Jiří Burda. "Corrosive Effect of Wood Ash Produced by Biomass Combustion on Refractory Materials in a Binary Al–Si System." Materials 15, no. 16 (August 22, 2022): 5796. http://dx.doi.org/10.3390/ma15165796.
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In terms of its chemical composition, biomass is a very complex type of fuel. Its combustion leads to the formation of materials such as alkaline ash and gases, and there is evidence of the corrosive effect this process has on refractory linings, thus shortening the service life of the combustion unit. This frequently encountered process is known as “alkaline oxidative bursting”. Corrosion is very complex, and it has not been completely described yet. Alkaline corrosion is the most common cause of furnace-lining degradation in aggregates that burn biomass. This article deals with an experiment investigating the corrosion resistance of 2 types of refractory materials in the Al2O3-SiO2 binary system, for the following compositions: I. (53 wt.% SiO2/42 wt.% Al2O3) and II. (28 wt.% SiO2/46 wt.% Al2O3/12 wt.% SiC). These were exposed to seven types of ash obtained from one biomass combustion company in the Czech Republic. The chemical composition of the ash is a good indicator of the problematic nature of a type of biomass. The ashes were analyzed by X-ray diffraction and X-ray fluorescence. Analysis confirmed that ash composition varies. The experiment also included the calculation of the so-called “slagging/fouling index” (I/C, TA, Sr, B/A, Fu, etc.), which can be used to estimate the probability of slag formation in combustion units. The corrosive effect on refractory materials was evaluated according to the norm ČSN P CEN/TS 15418, and a static corrosion test was used to investigate sample corrosion.
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Bentivenga, C., N. E. Politi, A. Bragagni, E. R. Cosentino, F. A. G. Cicero, M. Reta, and C. Borghi. "AB0390 OVERACTIVATION OF THE RENIN ANGIOTENSIN SYSTEM AS A POSSIBLE CONTRIBUTOR TO THE INCREASED CARDIOVASCULAR RISK IN RHEUMATOID ARTHRITIS (RA); EVALUATION OF LEUKOCYTE EXPRESSION OF ANGIOTENSIN II RECEPTOR TYPE 1 AND TYPE 2 IN A POPULATION OF RA PATIENTS." Annals of the Rheumatic Diseases 82, Suppl 1 (May 30, 2023): 1379.1–1379. http://dx.doi.org/10.1136/annrheumdis-2023-eular.5578.
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Backgroundrheumatoid arthritis (RA) is a chronic systemic autoinflammatory disease of unknown aetiology characterized by joint inflammation and multiple comorbidities, with a prevalence of approximately 1% of the adult population. It is considered an independent cardiovascular (CV) risk factor, in fact it is associated with significantly increased CV morbidity and mortality. The renin angiotensin system (RAS) is a hormonal cascade with pleiotropic effects. Not only is it crucial in blood pressure regulation but it also plays an important role, among many other effects, in inflammation. High circulating levels of proinflammatory cytokines such as TNF-α and IL-6 are critical in the pathogenesis of RA as well as in determining increased CV morbidity and mortality among these patients. TNF-α and IL-6 activate the systemic and local RAS; in turn, Angiotensin II (Ang II) increases several proinflammatory cytokines among which TNF-α and IL-6. Therefore, a self-perpetuating vicious circle between RAS and cytokines is triggered. Activation of the classical RAS leads to Angiotensin II (Ang II) formation which binds to Ang II receptors type 1 (AT1R) and 2 (AT2R). RAS overactivation is essential in determining vascular inflammation and endothelial dysfunction through its proinflammatory and profibrotic effects.Objectivesto determine whether RAS activity is higher among RA patients.Methodsleukocyte AT1R and AT2R mRNA was extracted and measured by real-time polymerase chain reaction analysis (RT-PCR) from 18 RA patients with stable disease and no traditional CV risk factors (mean age 52.17±11.4) and 10 healthy controls (mean age 43.8±8.61). Intergroup comparisons were made using the Mann-Whitney U test.ResultsA significantly higher expression of AT1R was found in RA patients compared to healthy controls (p<0.01). Even though the finding did not reach statistical significance, AT2R expression was also higher in RA patients (p =0.072).Conclusionthe results suggest AT1R and possibly AT2R upregulation in RA patients, indicating that RAS overactivation could contribute to the increased CV risk observed in RA patients. If such findings are confirmed by further research, they could have important implications in terms of prevention and treatment strategies for RA patients as RA is associated with an elevated CV risk that is often overlooked and underdiagnosed in these populations.References[1]Moreira FRC, de Oliveira TA, Ramos NE, Abreu MAD, Simões E Silva AC. The role of renin angiotensin system in the pathophysiology of rheumatoid arthritis.Mol Biol Rep. 2021;48(9):6619-6629. doi:10.1007/s11033-021-06672-8[2]Chang Y, Wei W. Angiotensin II in inflammation, immunity and rheumatoid arthritis.Clin Exp Immunol. 2015;179(2):137-145. doi:10.1111/cei.12467[3]Hansildaar R, Vedder D, Baniaamam M, Tausche AK, Gerritsen M, Nurmohamed MT. Cardiovascular risk in inflammatory arthritis: rheumatoid arthritis and gout.Lancet Rheumatol. 2021;3(1):e58-e70. doi:10.1016/S2665-9913(20)30221-6Acknowledgements:NIL.Disclosure of InterestsNone Declared.
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Kang, Sung-Min. "Mycobacterium tuberculosis Rv0229c Shows Ribonuclease Activity and Reveals Its Corresponding Role as Toxin VapC51." Antibiotics 12, no. 5 (May 1, 2023): 840. http://dx.doi.org/10.3390/antibiotics12050840.
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The VapBC system, which belongs to the type II toxin–antitoxin (TA) system, is the most abundant and widely studied system in Mycobacterium tuberculosis. The VapB antitoxin suppresses the activity of the VapC toxin through a stable protein–protein complex. However, under environmental stress, the balance between toxin and antitoxin is disrupted, leading to the release of free toxin and bacteriostatic state. This study introduces the Rv0229c, a putative VapC51 toxin, and aims to provide a better understanding of its discovered function. The structure of the Rv0229c shows a typical PIN-domain protein, exhibiting an β1-α1-α2-β2-α3-α4-β3-α5-α6-β4-α7-β5 topology. The structure-based sequence alignment showed four electronegative residues in the active site of Rv0229c, which is composed of Asp8, Glu42, Asp95, and Asp113. By comparing the active site with existing VapC proteins, we have demonstrated the justification for naming it VapC51 at the molecular level. In an in vitro ribonuclease activity assay, Rv0229c showed ribonuclease activity dependent on the concentration of metal ions such as Mg2+ and Mn2+. In addition, magnesium was found to have a greater effect on VapC51 activity than manganese. Through these structural and experimental studies, we provide evidence for the functional role of Rv0229c as a VapC51 toxin. Overall, this study aims to enhance our understanding of the VapBC system in M. tuberculosis.
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Zhang, Yan, Luyi Huang, Jie Li, Zhuo Dong, Qiang Yu, Ting Lei, Cheng Chen, et al. "Two-dimensional Ta2NiSe5/GaSe van der Waals heterojunction for ultrasensitive visible and near-infrared dual-band photodetector." Applied Physics Letters 120, no. 26 (June 27, 2022): 261101. http://dx.doi.org/10.1063/5.0093745.
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Dual-band photodetectors have attracted intensive attention because of the requirement of multiband information [such as visible (VIS) and near-infrared (NIR)] in multicolor imaging technology, in which additional information beyond human vision could assist object identification and navigations. The use of 2D materials can break the limitation of high cost of conventional epitaxial semiconductors and a complex cryogenic cooling system for multi-band detection, but there is still much room to improve the performance, especially in responsivity and signal noise ratio. Herein, we have fabricated a VIS-NIR dual-band photodetector based on a multilayer Ta2NiSe5/GaSe heterojunction. Benefiting from the type-II heterojunction, the separation of photo-induced carriers is naturally enhanced, which promotes the responsivity of this dual-band photodetector to 4.8 A W−1 (VIS) and 0.15 A W−1 (NIR) at room temperature with a suppressed dark current at ∼4 pA. Our work suggests that the Ta2NiSe5/GaSe heterostructure is a promising candidate for ultrasensitive VIS-NIR dual-band photodetection.