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Fellner, Matthias, Benoît Desguin, Robert P. Hausinger et Jian Hu. « Structural insights into the catalytic mechanism of a sacrificial sulfur insertase of the N-type ATP pyrophosphatase family, LarE ». Proceedings of the National Academy of Sciences 114, no 34 (7 août 2017) : 9074–79. http://dx.doi.org/10.1073/pnas.1704967114.
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The lar operon in Lactobacillus plantarum encodes five Lar proteins (LarA/B/C/D/E) that collaboratively synthesize and incorporate a niacin-derived Ni-containing cofactor into LarA, an Ni-dependent lactate racemase. Previous studies have established that two molecules of LarE catalyze successive thiolation reactions by donating the sulfur atom of their exclusive cysteine residues to the substrate. However, the catalytic mechanism of this very unusual sulfur-sacrificing reaction remains elusive. In this work, we present the crystal structures of LarE in ligand-free and several ligand-bound forms, demonstrating that LarE is a member of the N-type ATP pyrophosphatase (PPase) family with a conserved N-terminal ATP PPase domain and a unique C-terminal domain harboring the putative catalytic site. Structural analysis, combined with structure-guided mutagenesis, leads us to propose a catalytic mechanism that establishes LarE as a paradigm for sulfur transfer through sacrificing its catalytic cysteine residue.
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Fellner, Matthias, Joel A. Rankin, Benoît Desguin, Jian Hu et Robert P. Hausinger. « Analysis of the Active Site Cysteine Residue of the Sacrificial Sulfur Insertase LarE from Lactobacillus plantarum ». Biochemistry 57, no 38 (29 août 2018) : 5513–23. http://dx.doi.org/10.1021/acs.biochem.8b00601.
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Leimkühler, Silke, et Werner Klipp. « Role of XDHC in Molybdenum Cofactor Insertion into Xanthine Dehydrogenase of Rhodobacter capsulatus ». Journal of Bacteriology 181, no 9 (1 mai 1999) : 2745–51. http://dx.doi.org/10.1128/jb.181.9.2745-2751.1999.
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ABSTRACT Rhodobacter capsulatus xanthine dehydrogenase (XDH) is composed of two subunits, XDHA and XDHB. Immediately downstream ofxdhB, a third gene was identified, designatedxdhC, which is cotranscribed with xdhAB. Interposon mutagenesis revealed that the xdhC gene product is required for XDH activity. However, XDHC is not a subunit of active XDH, which forms an α2β2 heterotetramer inR. capsulatus. It was shown that XDHC neither is a transcriptional regulator for xdh gene expression nor influences XDH stability. To analyze the function of XDHC for XDH inR. capsulatus, inactive XDH was purified from anxdhC mutant strain. Analysis of the molybdenum cofactor content of this enzyme demonstrated that in the absence of XDHC, no molybdopterin cofactor MPT is present in the XDHAB tetramer. In contrast, absorption spectra of inactive XDH isolated from thexdhC mutant revealed the presence of iron-sulfur clusters and flavin adenine dinucleotide, demonstrating that XDHC is not required for the insertion of these cofactors. The absence of MPT from XDH isolated from an xdhC mutant indicates that XDHC either acts as a specific MPT insertase or might be a specific chaperone facilitating the insertion of MPT and/or folding of XDH during or after cofactor insertion.
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Wunsch, Patrick, Margitta Herb, Hagen Wieland, Ulrike M. Schiek et Walter G. Zumft. « Requirements for CuA and Cu-S Center Assembly of Nitrous Oxide Reductase Deduced from Complete Periplasmic Enzyme Maturation in the Nondenitrifier Pseudomonas putida ». Journal of Bacteriology 185, no 3 (1 février 2003) : 887–96. http://dx.doi.org/10.1128/jb.185.3.887-896.2003.
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ABSTRACT Bacterial nitrous oxide (N2O) reductase is the terminal oxidoreductase of a respiratory process that generates dinitrogen from N2O. To attain its functional state, the enzyme is subjected to a maturation process which involves the protein-driven synthesis of a unique copper-sulfur cluster and metallation of the binuclear CuA site in the periplasm. There are seven putative maturation factors, encoded by nosA, nosD, nosF, nosY, nosL, nosX, and sco. We wanted to determine the indispensable proteins by expressing nos genes from Pseudomonas stutzeri in the nondenitrifying organism Pseudomonas putida. An in silico study of denitrifying bacteria revealed that nosL, nosX (or a homologous gene, apbE), and sco, but not nosA, coexist consistently with the N2O reductase structural gene and other maturation genes. Nevertheless, we found that expression of only three maturation factors (periplasmic protein NosD, cytoplasmic NosF ATPase, and the six-helix integral membrane protein NosY) together with nosRZ in trans was sufficient to produce catalytically active holo-N2O reductase in the nondenitrifying background. We suggest that these obligatory factors are required for Cu-S center assembly. Using a mutational approach with P. stutzeri, we also studied NosA, the Cu-containing outer membrane protein previously thought to have Cu insertase function, and ScoP, a putative membrane-anchored chaperone for CuA metallation. Both of these were found to be dispensable elements for N2O reductase biosynthesis. Our experimental and in silico data were integrated in a model of N2O reductase maturation.
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Rudenko, Tatyana S., Sergey V. Tarlachkov, Nikolay D. Shatskiy et Margarita Yu Grabovich. « Comparative Genomics of Beggiatoa leptomitoformis Strains D-401 and D-402T with Contrasting Physiology But Extremely High Level of Genomic Identity ». Microorganisms 8, no 6 (19 juin 2020) : 928. http://dx.doi.org/10.3390/microorganisms8060928.
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Representatives of filamentous colorless sulfur-oxidizing bacteria often dominate in sulfide biotopes, preventing the diffusion of toxic sulfide into the water column. One of the most intriguing groups is a recently described Beggiatoa leptomitoformis including strains D-401 and D-402T. Both strains have identical genes encoding enzymes which are involved in the oxidation of hydrogen sulfide and thiosulfate. Surprisingly, the B. leptomitoformis strain D-401 is not capable to grow lithotrophically in the presence of reduced sulfur compounds and to accumulate elemental sulfur inside the cells, in contrast to the D-402T strain. In general, genomes of D-401 and D-402T have an extremely high level of identity and only differ in 1 single-letter substitution, 4 single-letter indels, and 16 long inserts. Among long inserts, 14 are transposons. It was shown that in the D-401 strain, a gene coding for a sulfur globule protein was disrupted by one of the mentioned transposons. Based on comparative genomics, RT-qPCR, and HPLC-MS/MS, we can conclude that this gene plays a crucial role in the formation of the sulfur globules inside the cells, and the disruption of its function prevents lithotrophic growth of B. leptomitoformis in the presence of reduced sulfur compounds.
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Ye, Ke-Yin, Markus Bursch, Zheng-Wang Qu, Constantin G. Daniliuc, Stefan Grimme, Gerald Kehr et Gerhard Erker. « Reversible formylborane/SO2coupling at a frustrated Lewis pair framework ». Chemical Communications 53, no 3 (2017) : 633–35. http://dx.doi.org/10.1039/c6cc07071j.
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Paietta, J. V., R. A. Akins, A. M. Lambowitz et G. A. Marzluf. « Molecular cloning and characterization of the cys-3 regulatory gene of Neurospora crassa. » Molecular and Cellular Biology 7, no 7 (juillet 1987) : 2506–11. http://dx.doi.org/10.1128/mcb.7.7.2506.
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The regulatory gene cys-3+ controls the synthesis of a number of enzymes involved in sulfur metabolism. cys-3 mutants show a multiple loss of enzymes in different pathways of sulfur metabolism. The cys-3+ gene was isolated by transformation of an aro-9 qa-2 cys-3 inl strain with a clone bank followed by screening with the "sib selection" method. The library used (pRAL1) contained inserts of Sau3a partial digest fragments of about 9 kilobases as well as the Neurospora qa-2+ gene. Double selection for qa-2+ and cys-3+ function was carried out. The transformants obtained with the isolated cys-3+ clone show recovery of the enzyme activities associated with the cys-3 mutation (e.g., arylsulfatase and sulfate permease). Restriction fragment length polymorphism experiments confirmed the identity of the clone, mRNA studies with Northern blots show that the expression of the cys-3+ gene is inducible. In contrast to cys-3+, the cys-3 (P22) mutant gene was not expressed at a higher level under sulfur-derepressed conditions.
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Timina, Olga, Oleg Timin et Anna Stepanova. « Some biochemical characteristics of the hairy roots of Pisum sativum L. mutants ». Ecological genetics 21, no 3S (4 décembre 2023) : 40. http://dx.doi.org/10.17816/ecogen568310.
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Two high-protein root cultures of vegetable pea mutants were received [1]. In continuation a PCR analysis of the obtained root cultures genes was carried out according [2] and the amino acid composition of the cultures protein was clarified in a dry product on the AAA 339TM device [3]. Obtained results confirmed the absence of rhizobia contamination of the cultures, which grow steadily on a hormone-free media for 5 years. PCR analysis revealed that fourrolgenesA,B,C,Dwere inserted into the genome of the root culture with genotypeafaftltl, and two —rol Candrol D— in the genome of the root culture with genotypetltl. The protein composition of the obtained cultures was represented by essential and non-essential amino acids and some others. In four inserts culture, the content of essential, ketogenic, proteinogenic and sulfur-containing amino acids prevailed by 1.5–2 times. Two inserts culture has twice as much aspartic acid and proline. Both cultures lacked tryptophan. The number of inserts determines the amino acid composition most likely.
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Pinto, Rachel, Joseph S. Harrison, Tsungda Hsu, William R. Jacobs et Thomas S. Leyh. « Sulfite Reduction in Mycobacteria ». Journal of Bacteriology 189, no 18 (20 juillet 2007) : 6714–22. http://dx.doi.org/10.1128/jb.00487-07.
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ABSTRACT Mycobacterium tuberculosis places an enormous burden on the welfare of humanity. Its ability to grow and its pathogenicity are linked to sulfur metabolism, which is considered a fertile area for the development of antibiotics, particularly because many of the sulfur acquisition steps in the bacterium are not found in the host. Sulfite reduction is one such mycobacterium-specific step and is the central focus of this paper. Sulfite reduction in Mycobacterium smegmatis was investigated using a combination of deletion mutagenesis, metabolite screening, complementation, and enzymology. The initial rate parameters for the purified sulfite reductase from M. tuberculosis were determined under strict anaerobic conditions [k cat = 1.0 (±0.1) electron consumed per second, and Km(SO3 −2) = 27 (±1) μM], and the enzyme exhibits no detectible turnover of nitrite, which need not be the case in the sulfite/nitrite reductase family. Deletion of sulfite reductase (sirA, originally misannotated nirA) reveals that it is essential for growth on sulfate or sulfite as the sole sulfur source and, further, that the nitrite-reducing activities of the cell are incapable of reducing sulfite at a rate sufficient to allow growth. Like their nitrite reductase counterparts, sulfite reductases require a siroheme cofactor for catalysis. Rv2393 (renamed che1) resides in the sulfur reduction operon and is shown for the first time to encode a ferrochelatase, a catalyst that inserts Fe2+ into siroheme. Deletion of che1 causes cells to grow slowly on metabolites that require sulfite reductase activity. This slow-growth phenotype was ameliorated by optimizing growth conditions for nitrite assimilation, suggesting that nitrogen and sulfur assimilation overlap at the point of ferrochelatase synthesis and delivery.
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Douglas, Paul, Marco Kriek, Penny Bryant et Peter L. Roach. « Lipoyl Synthase Inserts Sulfur Atoms into an Octanoyl Substrate in a Stepwise Manner ». Angewandte Chemie 118, no 31 (4 août 2006) : 5321–23. http://dx.doi.org/10.1002/ange.200601910.
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Douglas, Paul, Marco Kriek, Penny Bryant et Peter L. Roach. « Lipoyl Synthase Inserts Sulfur Atoms into an Octanoyl Substrate in a Stepwise Manner ». Angewandte Chemie International Edition 45, no 31 (4 août 2006) : 5197–99. http://dx.doi.org/10.1002/anie.200601910.
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Martinez Krahmer, D., S. Hameed, A. J. Sánchez Egea, D. Pérez, J. Canales et L. N. López de Lacalle. « Wear and MnS Layer Adhesion in Uncoated Cutting Tools When Dry and Wet Turning Free-Cutting Steels ». Metals 9, no 5 (12 mai 2019) : 556. http://dx.doi.org/10.3390/met9050556.
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Free-cutting steels are developed to produce large quantities of parts with low mechanical behavior, mainly for automotive sector. These alloys contain phosphorous, lead, sulfur, and manganese that help to improve the machinability and surface roughness. However, due to the toxicity of lead, steel mills in recent years have been focusing on non-toxic steels to produce minimum environmental pollution and better machinability. The present work investigates the tool wear during dry and wet turning of free-cutting steels (SAE 1212, SAE 12L14, and SAE 1215) by using uncoated hard metal inserts at three cutting speeds. Additionally, a EDS analysis was performed to determine the presence of Mn and S elements at the rake face of the cutting tool that can induce a higher adhesion of manganese sulfide (MnS). The results show that the SAE 12L14 steel has the best performance in terms of tool life at different cutting speeds. This difference is maximum at the lowest cutting speed, which gradually decreases with the increase of the cutting speed. The wear behavior is evaluated in the three steel alloys at each cutting speed and, consequently, the tool wear exhibits a slightly better performance in the dry machining condition for higher cutting speeds (180 and 240 m/min), independent of the steel alloy. Finally, EDS analysis confirms the presence of Mn and S elements at the rake face of the inserts machined in dry condition. Hence, MnS is expected to interpose between the machined surface and cutting tool surface to behave similar to tribofilm by reducing the wear on the cutting edge.
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Poli, Antoine, Caroline Schmitt, Boualem Moulouel, Arienne Mirmiran, Hervé Puy, Thibaud Lefèbvre et Laurent Gouya. « Iron, Heme Synthesis and Erythropoietic Porphyrias : A Complex Interplay ». Metabolites 11, no 12 (23 novembre 2021) : 798. http://dx.doi.org/10.3390/metabo11120798.
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Erythropoietic porphyrias are caused by enzymatic dysfunctions in the heme biosynthetic pathway, resulting in porphyrins accumulation in red blood cells. The porphyrins deposition in tissues, including the skin, leads to photosensitivity that is present in all erythropoietic porphyrias. In the bone marrow, heme synthesis is mainly controlled by intracellular labile iron by post-transcriptional regulation: translation of ALAS2 mRNA, the first and rate-limiting enzyme of the pathway, is inhibited when iron availability is low. Moreover, it has been shown that the expression of ferrochelatase (FECH, an iron-sulfur cluster enzyme that inserts iron into protoporphyrin IX to form heme), is regulated by intracellular iron level. Accordingly, there is accumulating evidence that iron status can mitigate disease expression in patients with erythropoietic porphyrias. This article will review the available clinical data on how iron status can modify the symptoms of erythropoietic porphyrias. We will then review the modulation of heme biosynthesis pathway by iron availability in the erythron and its role in erythropoietic porphyrias physiopathology. Finally, we will summarize what is known of FECH interactions with other proteins involved in iron metabolism in the mitochondria.
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Plumb, Jason J., Joanne Bell et David C. Stuckey. « Microbial Populations Associated with Treatment of an Industrial Dye Effluent in an Anaerobic Baffled Reactor ». Applied and Environmental Microbiology 67, no 7 (1 juillet 2001) : 3226–35. http://dx.doi.org/10.1128/aem.67.7.3226-3235.2001.
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ABSTRACT Fluorescent in situ hybridization (FISH) using 16S and 23S rRNA-targeted probes together with construction of an archaeal 16S ribosomal DNA (rDNA) clone library was used to characterize the microbial populations of an anaerobic baffled reactor successfully treating industrial dye waste. Wastewater produced during the manufacture of food dyes containing several different azo and other dye compounds was decolorized and degraded under sulfidogenic and methanogenic conditions. Use of molecular methods to describe microbial populations showed that a diverse group of Bacteria andArchaea was involved in this treatment process. FISH enumeration showed that members of the gamma subclass of the classProteobacteria and bacteria in theCytophaga-Flexibacter-Bacteroides phylum, together with sulfate-reducing bacteria, were prominent members of a mixed bacterial population. A combination of FISH probing and analysis of 98 archaeal 16S rDNA clone inserts revealed that together with the bacterial population, a methanogenic population dominated byMethanosaeta species and containing species ofMethanobacterium and Methanospirillum and a relatively unstudied methanogen, Methanomethylovorans hollandica, contributed to successful anaerobic treatment of the industrial waste. We suggest that sulfate reducers, or more accurately sulfidogenic bacteria, together with M. hollandicacontribute considerably to the treatment process through metabolism of dye-associated sulfonate groups and subsequent conversion of sulfur compounds to carbon dioxide and methane.
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Sirenko, К. A., V. L. Mazur et D. О. Derecha. « Dependence of hardness and other properties of gray iron on its carbon equivalent and degree of eutecticity ». Metal and Casting of Ukraine 31, no 2 (2023) : 42–50. http://dx.doi.org/10.15407/steelcast2023.02.042.
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The chemical composition, carbon equivalent and properties of castings from unalloyed and low-alloyed gray irons with lamellar graphite of various grades from СЧ100 to СЧА400 were analyzed in accordance with DSTU 8833:2019. There is a reference to such cast iron in the technical conditions for brake pads made of composite materials (rubber mixtures), in particular, for the production of cast iron inserts. Other products for railway transport are also made from cast iron СЧ350, for example, the friction “Khanin wedge”. It is shown that in industrial batches of the “Khanin wedge”, cast from cast iron СЧ350, the hardness did not correlate either with the content of elements in the chemical composition of the cast iron, or with the carbon equivalent due to the narrow range of its values even within the cast iron of the same grade. According to DSTU 8833:2019, with an increase in the carbon equivalent in the possible regulated range of values (%) from 3.03 to 4.54, the Brinell hardness of HB monotonically decreases by approximately 1.54...1.57, and the coefficient of thermal conductivity increases by almost one and a half times. Reducing the sulfur content in the chemical composition from 0.20 to 0.05 % of CH350 cast iron significantly reduces the range of dispersion of the carbon equivalent. The parameters (mean values, mean square deviations and coefficients of variation) of the carbon equivalent and the degree of eutecticity of the chemical composition of cast irons with lamellar graphite of brands from СЧ100 to СЧА400 were determined by means of statistical tests using the Monte Carlo method. It is shown that due to the significant dispersion of the values of the carbon equivalent of the chemical composition, hardness, coefficient of thermal conductivity, strength, density, modulus of elasticity, linear shrinkage, heat capacity, coefficient of linear expansion of cast iron with lamellar graphite of grades from СЧ100 to СЧА400 according to DSTU 8833:2019, it is necessary from the specified list grades of cast iron to determine and regulate in the technical conditions for composite brake pads a specific grade of cast iron intended for the manufacture of inserts in such pads.
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Monteiro, Jomar Patrício, Karl V. Clemons, Laurence F. Mirels, John A. Coller, Thomas D. Wu, Jata Shankar, Catalina R. Lopes et David A. Stevens. « Genomic DNA microarray comparison of gene expression patterns in Paracoccidioides brasiliensis mycelia and yeasts in vitro ». Microbiology 155, no 8 (1 août 2009) : 2795–808. http://dx.doi.org/10.1099/mic.0.027441-0.
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Paracoccidioides brasiliensis is a thermally dimorphic fungus, and causes the most prevalent systemic mycosis in Latin America. Infection is initiated by inhalation of conidia or mycelial fragments by the host, followed by further differentiation into the yeast form. Information regarding gene expression by either form has rarely been addressed with respect to multiple time points of growth in culture. Here, we report on the construction of a genomic DNA microarray, covering approximately 25 % of the genome of the organism, and its utilization in identifying genes and gene expression patterns during growth in vitro. Cloned, amplified inserts from randomly sheared genomic DNA (gDNA) and known control genes were printed onto glass slides to generate a microarray of over 12 000 elements. To examine gene expression, mRNA was extracted and amplified from mycelial or yeast cultures grown in semi-defined medium for 5, 8 and 14 days. Principal components analysis and hierarchical clustering indicated that yeast gene expression profiles differed greatly from those of mycelia, especially at earlier time points, and that mycelial gene expression changed less than gene expression in yeasts over time. Genes upregulated in yeasts were found to encode proteins shown to be involved in methionine/cysteine metabolism, respiratory and metabolic processes (of sugars, amino acids, proteins and lipids), transporters (small peptides, sugars, ions and toxins), regulatory proteins and transcription factors. Mycelial genes involved in processes such as cell division, protein catabolism, nucleotide biosynthesis and toxin and sugar transport showed differential expression. Sequenced clones were compared with Histoplasma capsulatum and Coccidioides posadasii genome sequences to assess potentially common pathways across species, such as sulfur and lipid metabolism, amino acid transporters, transcription factors and genes possibly related to virulence. We also analysed gene expression with time in culture and found that while transposable elements and components of respiratory pathways tended to increase in expression with time, genes encoding ribosomal structural proteins and protein catabolism tended to sharply decrease in expression over time, particularly in yeast. These findings expand our knowledge of the different morphological forms of P. brasiliensis during growth in culture.
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Ma, Zhong-Min, Joseph Dutra, Linda Fritts et Christopher J. Miller. « Lymphatic Dissemination of Simian Immunodeficiency Virus after Penile Inoculation ». Journal of Virology 90, no 8 (10 février 2016) : 4093–104. http://dx.doi.org/10.1128/jvi.02947-15.
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ABSTRACTThe human immunodeficiency virus (HIV) is primarily transmitted by heterosexual contact, and approximately equal numbers of men and women worldwide are infected with the virus. Understanding the biology of HIV acquisition and dissemination in men exposed to the virus by insertive penile intercourse is likely to help with the rational design of vaccines that can limit or prevent HIV transmission. To characterize the target cells and dissemination pathways involved in establishing systemic simian immunodeficiency virus (SIV) infection, we necropsied male rhesus macaques at 1, 3, 7, and 14 days after penile SIV inoculation and quantified the levels of unspliced SIV RNA and spliced SIV RNA in tissue lysates and the number of SIV RNA-positive cells in tissue sections. We found that penile (glans, foreskin, coronal sulcus) T cells and, to a lesser extent, macrophages and dendritic cells are primary targets of infection and that SIV rapidly reaches the regional lymph nodes. At 7 days after inoculation, SIV had disseminated to the blood, systemic lymph nodes, and mucosal lymphoid tissues. Further, at 7 days postinoculation (p.i.), spliced SIV RNA levels were the highest in the genital lymph nodes, indicating that this is the site where the infection is initially amplified. By 14 days p.i., spliced SIV RNA levels were high in all tissues, but they were the highest in the gastrointestinal tract, indicating that the primary site of virus replication had shifted from the genital lymph nodes to the gut. The stepwise pattern of virus replication and dissemination described here suggests that vaccine-elicited immune responses in the genital lymph nodes could help prevent infection after penile SIV challenge.IMPORTANCETo be the most effective, vaccines should produce antiviral immune responses in the anatomic sites of virus replication. Thus, understanding the path taken by HIV from the mucosal surfaces, which are the site of virus exposure, to the deeper tissues where the virus replicates will provide insight into where AIDS vaccines should produce immunity to be the most effective. In this study, we determined that, by day 7 after penile inoculation, SIV has moved first to the inguinal lymph nodes and replicates to high levels. Although the virus is widely disseminated to other tissues by day 7, replication is largely limited to the inguinal lymph nodes. The step-by-step movement of SIV from penile mucosal surfaces to the draining lymph nodes may allow an HIV vaccine that produces immunity in these lymph nodes to block HIV from establishing an infection in an exposed person.
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Rahim, Irwan Ridwan, Evi Aprianti, Faizal Arya Samman et Sutami Suparmin. « Potential Utilization of PT Vale Indonesia Tbk Slag as An Alternative Energy Source ». Jurnal Teknologi Lingkungan 23, no 2 (31 juillet 2022) : 189–97. http://dx.doi.org/10.29122/jtl.v23i2.5095.
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ABSTRAK Potensi pertambangan nikel di Indonesia tersebar dari Pulau Sulawesi, Maluku, dan Papua dengan sumber daya dan cadangan biji nikel laterit sebesar 4,2 milyar ton. Dampak negatifnya adalah dihasilkan limbah dari pengolahan bijih nikel yaitu terak (slag) dalam jumlah besar dan jika tidak dilakukan pengelolaan dengan baik, maka akan mengancam lingkungan sekitar pertambangan. Penelitian ini bertujuan untuk melakukan analisis SWOT kelayakan terak nikel yang dihasilkan oleh PT. Vale Indonesia Tbk menjadi sebuah produk energi alternatif dalam bentuk baterai dengan metode mengambil sampel terak dari ke-5 lokasi pada Tempat Penyimpanan Sementara (TPS) Delaney, PT Vale Indonesia Tbk. Selanjutnya, sampel terak dihaluskan sampai mencapai ukuran 100 mesh dan diberikan empat perlakuan elektrolit yaitu kering, air distilasi, hidrogen klorida (HCl), dan natrium hidroksida (NaOH). Setiap sampel terak yang telah diberikan perlakuan selanjutnya dimasukkan ke dalam wadah (sel) dengan ukuran 10x10x2 sentimeter kemudian memasukkan plat elektroda tembaga (Cu) dan seng (Zn) pada sisi sel yang berlawanan. Eksperimen terhadap 20 sel baterai menghasilkan data tegangan rata-rata tertinggi sebesar 1,28 Volt dengan arus rata-rata tertinggi sebesar 57,34 miliAmpere. Perlakuan yang paling efektif adalah dengan penambahan natrium hidroksida (NaOH) ke dalam baterai terak. Unsur yang berpengaruh dalam menghasilkan tegangan dan arus tertinggi adalah besi (Fe) dan senyawa oksida sulfat (SOx). Sel baterai terbukti dapat menyimpan energi listrik sebesar 0,1–24 kali arus dan tegangan awal melalui proses pengecasan sehingga disimpulkan bahwa baterai terak dapat dimanfaatkan sebagai sumber energi alternatif untuk alat elektronik berdaya rendah. Kata kunci: Terak nikel, Energi alternatif, Limbah, Baterai terak, Vale Indonesia ABSTRACT Nickel mining potential in Indonesia spreads from Sulawesi Island, Maluku, and Papua with resources and reserves of nickel laterite of 4.2 billion tons. The negative impact is that large amounts of waste are generated from nickel ore processing, namely slag and if not managed properly, it will threaten the environment around the mining. This study aims to conduct a SWOT (Strenght, Weakness, opportunity, Treat) analysis of the feasibility of nickel slag produced by PT. Vale Indonesia Tbk becoming an alternative energy production in the form of batteries by taking samples of slag from five locations at the Delaney Temporary Storage (TPS) of PT Vale Indonesia Tbk. Furthermore, the slag sample was pulverized until it reached a size of 100 mesh and given four electrolyte treatments; Dry, distilled water, hydrogen chloride (HCl), and sodium hydroxide (NaOH). Each slag sample that has been treated is then put into a container (cell) with a size of 10x10x2 centimeters then inserts the copper (Cu) and zinc (Zn) electrode plates on the opposite side of the cell. Experiments on 20 battery cells resulted in the highest average voltage data of 1.28 Volts with the highest average current of 57.34 milliamperes. The most effective treatment is the addition of sodium hydroxide (NaOH) into the slag battery. The elements that influence the production of the highest voltage and current are iron (Fe) and sulfate oxide (SOx) compounds. Battery cells are proven to be able to store electrical energy of 0.1–24 times the initial current and voltage through the charging process so it is concluded that the slag battery can be used as an alternative energy source for low-power electronic devices. Keywords: Nickel slag, Alternative energy, Waste, Battery slag, Vale Indonesia
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Zecchin, Paolo, Ludovic Pecqueur, Jonathan Oltmanns, Christophe Velours, Volker Schünemann, Marc Fontecave et Béatrice Golinelli‐Pimpaneau. « Structure‐based insights into the mechanism of [4Fe‐4S]‐dependent sulfur insertase LarE ». Protein Science, 15 décembre 2023. http://dx.doi.org/10.1002/pro.4874.
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AbstractSeveral essential cellular metabolites, such as enzyme cofactors, contain sulfur atoms and their biosynthesis requires specific thiolation enzymes. LarE is an ATP‐dependent sulfur insertase, which catalyzes the sequential conversion of the two carboxylate groups of the precursor of the lactate racemase cofactor into thiocarboxylates. Two types of LarE enzymes are known, one that uses a catalytic cysteine as a sacrificial sulfur donor, and the other one that uses a [4Fe‐4S] cluster as a cofactor. Only the crystal structure of LarE from Lactobacillus plantarum (LpLarE) from the first class has been solved. We report here the crystal structure of LarE from Methanococcus maripaludis (MmLarE), belonging to the second class, in the cluster‐free (apo‐) and cluster‐bound (holo‐) forms. The structure of holo‐MmLarE shows that the [4Fe‐4S] cluster is chelated by three cysteines only, leaving an open coordination site on one Fe atom. Moreover, the fourth non‐protein‐bonded iron atom was able to bind an anionic ligand such as a phosphate group or a chloride ion. Together with the spectroscopic analysis of holo‐MmLarE and the previously reported biochemical investigations of holo‐LarE from Thermotoga maritima, these crystal structures support the hypothesis of a reaction mechanism, in which the [4Fe‐4S] cluster binds a hydrogenosulfide ligand in place of the chloride anion, thus generating a [4Fe‐5S] intermediate, and transfers it to the substrate, as in the case of [4Fe‐4S]‐dependent tRNA thiolation enzymes.This article is protected by copyright. All rights reserved.
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Chatterjee, Shramana, Kristine F. Parson, Brandon T. Ruotolo, John McCracken, Jian Hu et Robert P. Hausinger. « Characterization of a [4Fe-4S]-dependent LarE sulfur insertase that facilitates nickel-pincer nucleotide cofactor biosynthesis in Thermotoga maritima ». Journal of Biological Chemistry, juin 2022, 102131. http://dx.doi.org/10.1016/j.jbc.2022.102131.
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Yuan, Shuai, Arif Yurdagul, A. Wayne Orr et Christopher G. Kevil. « Abstract 453 : Hydrogen Sulfide Increases Endothelial Permeability through Sulfane Sulfur Modification of Occludin ». Arteriosclerosis, Thrombosis, and Vascular Biology 35, suppl_1 (mai 2015). http://dx.doi.org/10.1161/atvb.35.suppl_1.453.
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Objective: Hydrogen sulfide (H2S) is an endogenous signaling molecule which exists in three biological pools, namely free H2S, sulfane sulfur and acid labile sulfur. H2S also regulates protein function by protein sulfuration. Fine tuning endothelial permeability is crucial for vascular functions. Therefore, we sought to determine how sulfane sulfur and sulfuration of cell junction proteins alters endothelial permeability. Methods: Endothelial permeability was evaluated by albumin leakage or transendothelial electrical resistance (TEER) in transwell inserts. Exogenous H2S was studied by treating human umbilical vein endothelial cells (HUVECs) with H2S donors including sodium sulfide (Na2S), diallyl trisulfide (DATS). To investigate the effect of endogenous H2S, endothelial cells were isolated from aorta (MAECs) of wild type and CSE knockout mice. Biological pools of H2S were measured using monobromobimane followed by detection of sulfide-dibimane with reverse phase HPLC. Protein sulfhydration is determined by 2-methylsulfonyl benzothiazole (MSBT)/cyanoacetate tag-switch assay. Results: DATS treatment elevated sulfane sulfur and induced rapid albumin leakage through HUVEC monolayer. Comparatively, Na2S increased permeability only at later time points and to a lesser extent. Total sulfide and sulfane sulfur were reduced in CSE deficient MAECs. Moreover, MAECs lacking CSE showed enhanced barrier function compared to wild-type MAECs, characterized by decreased albumin leakage and increased of TEER. The tag-switch assay showed increased sulfuration of occludin in HUVECs. In conclusion, H2S bioavailability regulates endothelial solute permeability.
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Marquez, Melissa D., Carina Greth, Anastasiya Buzuk, Yaxi Liu, Catharina M. Blinn, Simone Beller, Laura Leiskau et al. « Cytosolic iron–sulfur protein assembly system identifies clients by a C-terminal tripeptide ». Proceedings of the National Academy of Sciences 120, no 44 (26 octobre 2023). http://dx.doi.org/10.1073/pnas.2311057120.
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The eukaryotic cytosolic Fe–S protein assembly (CIA) machinery inserts iron–sulfur (Fe–S) clusters into cytosolic and nuclear proteins. In the final maturation step, the Fe–S cluster is transferred to the apo-proteins by the CIA-targeting complex (CTC). However, the molecular recognition determinants of client proteins are unknown. We show that a conserved [LIM]-[DES]-[WF]-COO – tripeptide is present at the C-terminus of more than a quarter of clients or their adaptors. When present, this targeting complex recognition (TCR) motif is necessary and sufficient for binding to the CTC in vitro and for directing Fe–S cluster delivery in vivo. Remarkably, fusion of this TCR signal enables engineering of cluster maturation on a nonnative protein via recruitment of the CIA machinery. Our study advances our understanding of Fe–S protein maturation and paves the way for bioengineering novel pathways containing Fe–S enzymes.
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Qu, Di, Peng Ge, Laure Botella, Sae Woong Park, Ha-Na Lee, Natalie Thornton, James M. Bean et al. « Mycobacterial biotin synthases require an auxiliary protein to convert dethiobiotin into biotin ». Nature Communications 15, no 1 (16 mai 2024). http://dx.doi.org/10.1038/s41467-024-48448-1.
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AbstractLipid biosynthesis in the pathogen Mycobacterium tuberculosis depends on biotin for posttranslational modification of key enzymes. However, the mycobacterial biotin synthetic pathway is not fully understood. Here, we show that rv1590, a gene of previously unknown function, is required by M. tuberculosis to synthesize biotin. Chemical–generic interaction experiments mapped the function of rv1590 to the conversion of dethiobiotin to biotin, which is catalyzed by biotin synthases (BioB). Biochemical studies confirmed that in contrast to BioB of Escherichia coli, BioB of M. tuberculosis requires Rv1590 (which we named “biotin synthase auxiliary protein” or BsaP), for activity. We found homologs of bsaP associated with bioB in many actinobacterial genomes, and confirmed that BioB of Mycobacteriumsmegmatis also requires BsaP. Structural comparisons of BsaP-associated biotin synthases with BsaP-independent biotin synthases suggest that the need for BsaP is determined by the [2Fe–2S] cluster that inserts sulfur into dethiobiotin. Our findings open new opportunities to seek BioB inhibitors to treat infections with M. tuberculosis and other pathogens.
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Day, Erin, Ronald M. Galiwango, Daniel Park, Sanja Huibner, Maliha Aziz, Aggrey Anok, James Nnamutete et al. « Insertive vaginal sex is associated with altered penile immunology and enrichment of Gardnerella vaginalis in uncircumcised Ugandan men ». American Journal of Reproductive Immunology 91, no 1 (6 décembre 2023). http://dx.doi.org/10.1111/aji.13801.
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AbstractProblemHIV susceptibility is linked to the penile immune milieu (particularly IL‐8 levels) and microbiome. The effects of insertive vaginal sex itself on penile immunology and microbiota are not well described.Method of studyWe compared the immune milieu and microbiology of the coronal sulcus (CS) and distal urethra in 47 uncircumcised Ugandan men reporting ever (n = 42) or never (n = 5) having had vaginal intercourse. Soluble immune factors were assayed by multiplex ELISA, and penile bacteria abundance by 16S rRNA qPCR and sequencing. Co‐primary endpoints were penile levels of IL‐8 and soluble E‐cadherin.ResultsIndependent of classical STIs, men reporting prior vaginal sex demonstrated elevated IL‐8 levels in both the coronal sulcus (1.78 vs. 0.81 log10 pg/mL, p = .021) and urethra (2.93 vs. 2.30 log10 pg/mL; p = .003), with a strong inverse relationship between urethral IL‐8 levels and the time from last vaginal sex (r = –0.436; p = .004). Vaginal sex was also associated with elevated penile IL‐1α/β and soluble E‐cadherin (sEcad), a marker of epithelial disruption. Gardnerella vaginalis (Gv) was only present in the penile microbiome of men reporting prior vaginal sex, and urethral Gv absolute abundance was strongly associated with urethral inflammation (r = 0.556; p < .001); corynebacteria were enriched in the CS of men reporting no prior vaginal sex and were associated with reduced CS inflammation.ConclusionsSexual intercourse was associated with sustained changes in penile immunology, potentially mediated through microbial alterations, in particular the urethral abundance of G. vaginalis. Future studies should further characterize the effects of sexual debut on penile bacteria and immunology.
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Shen, Steven R., Erin A. Boese, Courtney P. Clark, Xiaofei Man, Melisa Nika et Sayoko E. Moroi. « Acute Angle-Closure Crisis Secondary to Topiramate-Induced Ciliochoroidal Effusion With Underlying Plateau Iris Configuration ». Journal of Diagnostic Medical Sonography, 5 août 2021, 875647932110357. http://dx.doi.org/10.1177/87564793211035777.
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Objective: The development of ciliochoroidal effusions and secondary acute angle-closure crisis (AACC) is an uncommon side effect of topiramate, a common antiepileptic now FDA-approved for migraine prophylaxis. The mechanisms that underlie the development of ciliochoroidal effusions after topiramate use remain unclear. Materials and Methods: Ultrasound biomicroscopy (UBM) was also performed in all participants after stopping topiramate. Results: Six patient cases are presented with medication-induced AACC following the initiation or escalation of topiramate. Ciliochoroidal effusions were confirmed by gray-scale sonography in all patients at presentation. The images revealed either plateau iris configuration or atypical plateau iris configuration. Plateau iris configuration is defined by presence of an anteriorly rotated ciliary body processes and an absent posterior sulcus. Atypical plateau iris configuration refers to when the iris inserts directly into the ciliary body face. This case series, of medication-induced angle-closure crisis, suggests that plateau iris configuration is a shared anatomical feature in the development of topiramate-induced ciliochoroidal effusions.