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1
Lund, Victoria A. "Peptidoglycan dynamics in Staphylococcus aureus using super-resolution microscopy." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/13652/.
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Pereira, Pedro Matos. "Peptidoglycan assembly machines: The Staphylococcus aureus Penicillin-Binding Proteins." Doctoral thesis, Universidade Nova de Lisboa. Instituto de Tecnologia Química e Biológica, 2013. http://hdl.handle.net/10362/10884.
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Dissertation presented to obtain the Ph.D degree in BiologyThe bacterial cell wall (CW) is of critical importance to cell viability. Impairment of CW synthesis or integrity rapidly leads to cell lysis and death. As there is no equivalent structure to the bacterial CW in mammalian cells, many important antibiotics target the enzymes responsible for its synthesis. The scaffold of the CW consists of the polymer peptidoglycan (PGN), a meshlike structure composed of glycan strands cross‐linked by short peptides. The final steps of PGN synthesis are catalysed by the penicillin‐binding proteins (PBPs), which assemble lipid‐linked disaccharide peptide precursors of PGN into high molecular weight oligomers via transglycosylation and transpeptidation reactions. These proteins have been proposed to work in multi‐enzyme complexes that would also include CW hydrolases.(...)
3
Alorabi, J. A. "Role of peptidoglycan deacetylase in Staphylococcus aureus virulence and survival." Thesis, University of Liverpool, 2016. http://livrepository.liverpool.ac.uk/3002567/.
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Staphylococcus aureus is an opportunist human pathogen that colonises the anterior nares and is shed onto skin. The bacterium is most frequently a cause of skin and soft-tissue infections, yet is also a major cause of respiratory, urinary tract, bone, eye and brain infections. Evolution of the bacterium has selected strains that are more antibiotic resistant, particularly in the hospital environment and more recently in the community. The pathogen has the capacity for secreting a wide range of proteins that contribute to survival from host immunity and competing microflora. The bacterial cell wall is a vital structural polymer serving mechanical roles to protect bacteria from osmotic challenges and it serves as a scaffold for the attachment of many anchored proteins and anionic polymers for interaction with extracellular components. Peptidoglycan of S. aureus is modified by enzyme catalysed decoration of N-acetyl muramic acid with teichoic acid and O-acetylation which promotes lysozyme resistance. Further modification of teichoic acid engenders properties linked to colonisation and survival during the life-cycle. This research study sought to assign roles of S. aureus secreted proteins of unknown function using bioinformatics. From this approach the study identified a peptidoglycan deacetylase (Pgd) and this enzyme catalyses a reduction in acetylation of N-acetyl glucosamine in biosynthesis of the cell wall. An allelic replacement mutant revealed altered muropeptide composition that was consistent with its proposed N-deacetylase activity, and transmission electron microscopy (TEM) revealed a reduction in cell wall thickness. S. aureus pgd exhibited increased surface charge to influence a range of phenotypes, including autolysis, resistance and biofilm formation. Resistance was increased to lysozyme, and most notably there was rescue of the lysozyme sensitivity phenotype of an oatA mutant (lacking peptidoglycan O-acetyltransferase [oatA] activity). Hydrodynamic flow biofilm assay revealed that both S. aureus pgd and oatA mutants exhibited negligible biofilm formation on a glass surface; treatment of the surface with plasma fluid increased biofilm capability. Biofilms of S. aureus pgd cultured in static conditions revealed an opposite phenotype with a thicker, but loosely adherent biofilm. Confocal laser scanning microscopy (CSLM) combined with viability staining it was revealed that in the biofilm, there were increased dead cells compared with wild-type. An increased lag phase of growth of S. aureus pgd was identified, and quantitative label free proteomics was used to determine that multiple metabolism and cell wall proteins were differentially expressed, compared with the wild-type strain. The proteome analysis revealed that the pgd mutant expressed increased levels of the lytic transglycosylase, IsaA and this might explain the biofilm phenotype. Further contributions to the biofilm phenotype could be due to decreased expression of protein A and reduced pyruvate metabolism enzymes. S. aureus pgd was killed more rapidly in an opsonophagocytosis assay compared with its isogenic parent but showed equivalent levels of complement deposition and serum survival. Infection models of pneumonia and bacteraemia were tested and revealed reduced bacterial loads for lung and kidney, respectively. The S. aureus pgd mutant phenotype requires further study and it should provide insights into cell wall structure and function. Pgd could represent a future candidate vaccine antigen due to its likely cell surface exposure and contribution to key cellular processes.
4
Qiao, Yuan. "Reconstitution of the Final Step of Peptidoglycan Assembly in Staphylococcus aureus." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493392.
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Bacterial peptidoglycan (PG) is an exoskeleton structure that maintains cell shape and protects cells from lysis. Peptidoglycan is essential in bacteria but is not found in mammalian cells. Therefore, it is the target for several classes of antibiotics, including the beta-lactam family. Beta-lactams target the transpeptidase (TP) domain of penicillin-binding proteins (PBPs), the enzymes responsible for the final step of peptidoglycan biosynthesis. Mutations of transpeptidases in Staphylococcus aureus (S. aureus) have been implicated in beta-lactam resistance in the clinic (commonly known as MRSA infections). Despite the fact that PBPs are important antibiotic targets, there have been no direct assays to monitor their enzymatic activity, primarily due to inaccessibility to appropriate substrates. The PG precursor, Lipid II, is required to study transpeptidase activity. Lipid II contains a glycopeptide attached to a pyrophosphate lipid containing 55 carbons. It has poor physical properties and is present in low abundance in bacteria.
This thesis describes the reconstitution of peptidoglycan assembly in Staphylococcus aureus by the essential Class A PBP, PBP2. This was enabled by several key advances, which are also described. The first advance is the discovery that PBP4, a low-molecular weight PBP in S. aureus, can use a Lipid II analogue as a transpeptidation substrate. It can incorporate biotin-D-Lys (BDL) and other non-canonical D-amino acids into the terminal position of the stem peptide in Lipid II. BDL labeling of Lipid II with S. aureus PBP4 has enabled the second advance: the direct detection of native Lipid II extracted from bacteria. This has facilitated elucidation of cellular mechanisms of antibiotics that target cell wall biosynthesis. The third advance is a general strategy to accumulate and isolate native Lipid II in bacteria in useful quantities. Access to substantial quantities of native S. aureus Lipid II has enabled reconstitution of PBP2 transpeptidase activity, as well as characterization of several beta-lactam antibiotics by monitoring enzymatic inhibition.
In sum, this work establishes important tools for studying enzymatic mechanisms of bacterial transpeptidases and for characterizing inhibitors that target bacterial peptidoglycan biosynthesis.Chemical Biology
5
Wang, Hsin Jayaswal Radheshyam K. Wilkinson Brian J. "Molecular analysis of a Staphylococcus aureus gene encoding a peptidoglycan hydrolase activity." Normal, Ill. Illinois State University, 1991. http://wwwlib.umi.com/cr/ilstu/fullcit?p9219089.
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Thesis (Ph. D.)--Illinois State University, 1991.Title from title page screen, viewed January 5, 2006. Dissertation Committee: Radheshyam K. Jayaswal, Brian J. Wilkinson (co-chairs), Herman E. Brockman, Anthony J. Otsuka, Hou Tak Cheung. Includes bibliographical references (leaves 117-129) and abstract. Also available in print.
6
Dorling, Jack. "Peptidoglycan recycling in the Gram-positive bacterium Staphylococcus aureus and its role in host-pathogen interaction." Thesis, University of Oxford, 2018. http://ora.ox.ac.uk/objects/uuid:3fc4f926-296d-43a1-bb45-af9f37a87d8d.
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Bacteria are enclosed by a peptidoglycan sacculus, an exoskeleton-like polymer composed of glycan strands cross-linked by short peptides. The sacculus surrounds the cell in a closed bag-like structure and forms the main structural component of the bacterial cell wall. As bacteria grow and divide, cell wall remodelling by peptidoglycan hydrolases results in the release of peptidoglycan fragments from the sacculus. In Gram-negative bacteria, these fragments are efficiently trapped and recycled. Gram-positive bacteria however shed large quantities of peptidoglycan fragments into the environment. For nearly five decades, Gram-positive bacteria were thus assumed not to recycle peptidoglycan and this process has remained enigmatic until recently. In this thesis, the occurrence and physiological role of peptidoglycan recycling in the Gram-positive pathogen Staphylococcus aureus was investigated. S. aureus is an important pathogen, and is becoming increasingly resistant to many antibiotics. Through bioinformatic and experimental means it was determined that S. aureus may potentially recycle components of peptidoglycan and novel peptidoglycan recycling components were identified and characterised. Though disruption of putative peptidoglycan recycling in S. aureus appears not affect growth or gross morphology of this bacterium, potential roles for peptidoglycan recycling in cell wall homeostasis and in virulence were identified. This is to my knowledge the first demonstration of a potential role of peptidoglycan recycling in either of these aspects of bacterial physiology in any Gram-positive bacterium. This is an important step forward in understanding the basic biology of Gram-positive bacteria, and in understanding the mechanisms of virulence in S. aureus. Future study of this process in S. aureus and other Gram-positive bacteria promises to reveal yet further facets of this process and its functions, potentially leading to the identification of novel therapeutic approaches to combat infections.
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Sandhu, Sandeep. "Development of an antibody-based assay for methicillin resistant Staphylococcus aureus using synthetic peptidoglycan precursors." Thesis, University of Warwick, 2010. http://wrap.warwick.ac.uk/36857/.
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Methicillin-resistant Staphylococcus aureus (MRSA) are isolates of the bacterium Staphylococcus aureus that have acquired genes encoding antibiotic resistance to all penicillins, including methicillin and other narrow-spectrum β- lactamase-resistant penicillin antibiotics. Outbreaks of MRSA occur quite frequently as there is no quick screening test for the presence of MRSA. The aim of this project is to try and develop an antibody based detection test for rapid detection of MRSA, which could help in the prevention of outbreaks. An antigen (UDP-MurNAc-L-Ala-γ-D-Glu-L-Lys(ε-NH2-Gly)5-D-Ala-D-Ala) that resembles the outer surface of the Staphylococcus aureus (contains a Gly5 moiety that is specific for S. aureus) cell wall peptidoglycan has been prepared, and attached to a carrier protein. Sheep antibodies raised against this antigen were screened using ELISA assays. The results showed that antibodies did have specificity for the antigen. Cell walls were prepared from several different bacteria, including two MRSA and one methicillin-sensitive Staphylococcus aureus (MSSA) strain. ELISA assays using these cell walls showed that the antibodies had specificity for cell walls containing (Gly)5 in the order of S aureus (Gly5) > S. simulans (less Gly5) > S. pneumoniae (no Glyn) > E. coli (no Glyn, Gram-negative strain). A particularly high response was observed for one of the two MRSA strains, detectable at 0.1 μg of cell wall. An HPLC-based UV-Vis assay was developed to monitor the activity of peptidoglycan polymerisation enzymes from S. aureus, while preparing polymeric peptidoglycan as an antigen for immunisation. Several intermediates in peptidoglycan polymerisation were detected using S. aureus monofunctional glycosyltransferase (MGT), which allowed us to propose a new hypothesis for the early steps of peptidoglycan transglycosylation.
8
Lee, Yoon-Ik Wilkinson Brian J. Jayaswal Radheshyam K. "Cloning of a Staphylococcus aureus peptidoglycan hydrolase gene, and purification and characterization of the gene product." Normal, Ill. Illinois State University, 1993. http://wwwlib.umi.com/cr/ilstu/fullcit?p9323735.
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Thesis (Ph. D.)--Illinois State University, 1993.Title from title page screen, viewed February 13, 2006. Dissertation Committee: Brian J. Wilkinson, Radheshyam K. Jayaswal (co-chairs), Anthony E. Liberta, Herman E. Brockman, Hou Tak Cheung. Includes bibliographical references (leaves 115-124) and abstract. Also available in print.
9
Roberts, Erin. "Cytokine expression, cytoskeleton organization, and viability of SIM-A9 microglia exposed to Staphylococcus aureus-derived lipoteichoic acid and peptidoglycan." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1515329731281897.
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Blake, Katy Louise. "Characterisation of MurA and MurZ in staphylococcus aureus: Their role in peptidoglycan bisynthesis and potential as targets for novel inhibitors." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494156.
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String, Gabrielle. "The Effect of Gram-Positive Staphylococcus aureus Cell Wall Components Lipoteichoic Acid and Peptidoglycan on Cytokine production, Cytoskeletal Arrangement, and Cell Viability on RAW 264.7 Murine Macrophages." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright150126065655319.
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Korgaonkar, Aishwarya Kiran 1983. "A mechanism for interspecies competition and virulence in Pseudomonas aeruginosa-containing polymicrobial infections." Thesis, 2012. http://hdl.handle.net/2152/ETD-UT-2012-08-6202.
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Pseudomonas aeruginosa is a ubiquitous bacterium that is commonly isolated from soil and water. Additionally, this bacterium can cause infections in individuals with compromised immune systems and in those with underlying debilitating conditions. Individuals with cystic fibrosis, burn wounds, AIDS and diabetes are more likely to being infected by P. aeruginosa than healthy individuals. In individuals with CF, there is a marked increase in the accumulation of lung mucus that serves as a source of nutrition for P. aeruginosa and other bacterial species resulting in chronic and often fatal infections. While CF lung infections are initially caused by more than one species of bacteria, over time P. aeruginosa emerges as the dominant species. P. aeruginosa also causes chronic infections in association with other bacteria in wounds. Microbes within these infections are engaged in complex interactions with each other. Often, these interactions are synergistic resulting in infections that are recalcitrant to antimicrobial therapy. While many studies have documented the occurrence of synergistic polymicrobial infections, little is known about the molecular mechanisms prevailing in these infections.
Interestingly, production of virulence factors by P. aeruginosa has been shown to correlate with the presence of specific nutrients in their growth environment. Expanding on the idea of available nutrients affecting virulence, I demonstrate the ability of N-Acetylglucosamine (GlcNAc) and GlcNAc-containing polymers such as peptidoglycan to induce production of virulence factors in P. aeruginosa. Peptidoglycan shed by Gram-positive bacteria acts as a cue for P. aeruginosa in polymicrobial environments, to enhance production of virulence factors. In the context of a polymicrobial infection, this results in enhanced pathogenesis. Here, I provide insights into mechanisms influencing such interspecies interactions between the opportunistic pathogen Pseudomonas aeruginosa and S.aureus.text
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Figueiredo, Teresa Carla de Almeida. "Amidation of peptidoglycan in Staphylococcus aureus." Doctoral thesis, 2014. http://hdl.handle.net/10362/14147.
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Staphylococcus aureus is one of the most important contemporary human pathogens. The evolutionary “success” of this species is closely related to its remarkably capacity to acquire antibiotic resistance traits. In this perspective, it is important to extend our knowledge concerning the mechanisms of antibiotic resistance in S. aureus and to identify new antimicrobials targets.(...)Fundação Para a Ciência e a Tecnologia
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Covas, Gonçalo. "Synthesis and host recognition of Staphylococcus aureus peptidoglycan." Doctoral thesis, 2019. http://hdl.handle.net/10362/98834.
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"Bacteria are able to establish relationships with other organisms, which may be temporary, as in a bacterial infection, or long-term, as in symbiosis. From the interplay between different organisms emerged the concept of “identity”, i.e. the need to distinguish “self” from “non-self”. Multicellular organisms have developed immune systems responsible for the detection of “non-self” organisms that lead to the activation of appropriate responses to maintain the organism in a state of homeostasis. In opposition, bacteria have developed mechanisms (virulence factors) to avoid their identification as harmful, in order to assure their survival within the host. (...)"
15
Lin, Hsiao-Yun, and 林曉筠. "Staphylococcus aureus-derived peptidoglycan induces neuroinflammatory responses in microglia." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/82445609617880728936.
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碩士中國醫藥大學
基礎醫學研究所
98
Microglia are the phagocytes of central nervous system and involved in immune responses , providing an initial line defence against invading pathogens. Here we explored the effect of cell wall component of Gram positive bacteria , Staphylococcus aureus, on glia activation and neuroinflammation. In particular, we investigate the signaling pathways of iNOS, COX-2 and IL-6 production caused by Staphylococcus aureus-derived peptidoglycan (PGN) and it’s signal transduction. PGN increased iNOS and COX-2 mRNA and protein expression in concentration and time dependent manner. In addition, PGN also induced IL-1b, TNF-a and IL-6 mRNA over-expression. We further confirmed that PGN induced iNOS and COX-2 expression is mediated by TLR2/MyD88. On the other hand, PGN-induced iNOS and COX-2 up-regulation were also attenuated by PI3K inhibitors (LY294002 and wortmanin) and AKT inhibitor. Treatment of microglia with NF-kB inhibitor, PDTC, TPCK and Bay117082, inhibited PGN-induced iNOS and COX-2 expression. PGN also increased kB-luciferase activity in microglia. Our data demonstrate that PGN-induced iNOS, COX-2 and proinflammatory cytokine expression in microglia are mediated by the TLR2/MyD88 and PI3K/AKT pathways, which in turn initiate IKKa/b and NF-kB activation. Moreover, we investigated the signaling pathways involved in PGN-induced IL-6 production. PGN increased IL-6 mRNA and protein expression in microglia and rat primary culture microglia time-dependently. PGN also increased JNK activation and c-Jun phosphorylation. Pretreatment with JNK inhibitor (SP600125) and AP-1 inhibitors (Tanshinone IIA and curcumin) reduced PGN-induced IL-6 mRNA and protein expression. PGN also increased p-c-Jun and c-Fos translocation from cytosol to nucleus. In addition, PGN-increased binding activity of activator protein-1 (AP-1) transcription factor was determined by electrophoretic mobility shift assay (EMSA). Moreover, PGN-increased AP-1 binding activity was reduced by treatment with c-Fos- and c-Jun-neutralized antibody. PGN also increased IL-6 luciferase activity, which was attenuated by JNK inhibitor, AP-1 inhibitors and JNK dominant-negative mutant (JNK-DN). Taken together these data suggest that PGN increases IL-6 production in microglia are through the TLR2receptor/JNK /c-Jun and AP-1 signaling pathway. Our results provide a mechanism of PGN induce proinflammatory cytokine expression, which indicates that PGN plays an important role in microglia activation. With a further understanding of these signal transduction pathways, we can develop novel therapeutic strategies to reduce neuroinflammation caused by Gram-positive organisms.
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Cavaco, Gonçalo Francisco Cordeiro. "Peptidoglycan amidation of Staphylococcus aureus and bacteria cell physiology." Master's thesis, 2018. http://hdl.handle.net/10362/37048.
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Peptidoglycan is a highly dynamic macromolecule that undergoes several
secondary modifications during its biosynthesis. The MurT-GatD enzymatic complex is
necessary for the amidation of glutamate of the stem peptide of Staphylococcus aureus
peptidoglycan. This secondary modification influences critical processes of S. aureus,
such as growth rate, beta-lactam and lysozyme resistance. However, the mechanisms
through which it influences S. aureus physiology remain unknown.
In this study, several MRSA strains and respective murT-gatD mutants were
used. Since peptidoglycan is a surface-exposed macromolecule, we analyzed the
influence of peptidoglycan amidation on the modulation of the cell envelope, by
measuring the surface charge, through a cytochrome C association based method. For
all strains, peptidoglycan amidation was associated with a more positive surface charge.
Consequently, such impact could alter cell-cell aggregation and surface-adhesion
properties. Overall, amidation mutants showed either increased biofilm production or
formation of cell aggregates during planktonic growth; these two distinct phenotypes
seemed to be associated with the biofilm matrix composition of the parental strain. In
fact, amidation mutants of PIA-positive parental strains showed formation of cell
aggregates, whereas the ones of PIA-negative parental strains showed higher biofilm
production. Additionally, biofilm detaching assays showed that the composition of the
biofilm matrix is altered in response to lack of peptidoglycan amidation.
Peptidoglycan amidation was proposed to influence autolysis, by disturbing the
balance between the cell wall synthetic and hydrolytic machineries and/or by acting as a signal to regulate the activity of autolysins. Zymographic assays suggested that nonamidated peptidoglycan is a better substrate for autolysins. Moreover, these enzymes seemed to be less expressed/active in amidation mutants. Western Blot and promoter fusion assays confirmed that peptidoglycan amidation influences the autolytic system, as non-amidated mutants showed lower expression of ATL and SLEI autolysins.
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Gonçalves, Bárbara Vitorino. "A new antimicrobial target in Staphylococcus aureus – amidation of peptidoglycan." Master's thesis, 2014. http://hdl.handle.net/10362/14132.
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taphylococcus aureusis adangerousopportunistic pathogenwith a large number of virulence factors, responsible for a wide range of diseases. Its clinical importance is mainly due to itshigh capacity to accumulate resistance mechanismsto virtually all antibiotics. Over the last century,hugeeffortshavebeen dedicatedto the study of the molecular mechanisms underlying resistance of S. aureusto β-lactam antibiotics. Besides the exogenousmecAgene, identified as the main player of the mechanism of β-lactam resistance, several housekeeping geneswerealso identified to be requiredfor theoptimal expressionof resistance, the so-calledauxiliary genes. The use of combination agents in synergy with β-lactams has already proven to be efficient in restoring β-lactam activityagainst resistantstrains.Among the auxiliary genes, murT-gatDoperonwas recently identified as encoding for the enzymes responsible for amidation of the glutamate residue of peptidoglycan. Glutamate amidation, a secondary modification of peptidoglycan,is essential for S. aureusviability and is involved in the mechanisms of resistance to β-lactams and to lysozyme, being an excellent target for the development of new antimicrobial compounds.The purpose of this Master thesiswasto dynamically characterize the structure of MurT-GatD complex by Nuclear Magnetic Resonance (NMR). Structural information on the physical interaction between the two partner proteins will be an essential contribution for the future developmentofa compound that blocks MurT-GatD association. Such a compound would act in synergywith β-lactams, restoring S. aureus susceptibility. The results of this study identified the DUF1727 domain (C-terminal domain of MurT protein) as responsible for the interaction between MurT and GatD and also showed, through 1H-15N-spectrum NMR analysis,a strong interaction between DUF1727 and GatD protein.This work paved the way for the comprehensive analysis of MurT-GatD interaction.
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Biswas, Raja [Verfasser]. "Characterization of Staphylococcus aureus peptidoglycan hydrolases and isolation of defined peptidoglycan structures / von Raja Biswas." 2006. http://d-nb.info/983660638/34.
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Monteiro, João Miguel da Silva Queiroga. "Mechanisms coordinating peptidoglycan synthesis with the cell cycle in Staphylococcus aureus." Doctoral thesis, 2018. http://hdl.handle.net/10362/98063.
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"The emergence and spread of antibiotic resistance in bacteria
constitutes one of the major challenges to global public health and is
predicted to further escalate during the 21st century. One of the most
frequent multi-drug resistant pathogens is methicillin-resistant
Staphylococcus aureus (MRSA), a gram-positive coccoid bacterium that
causes difficult to treat infections with severe morbidity and
mortality rates. Many of the commonly used antibiotics target steps
in the biosynthesis of peptidoglycan (PG), a robust but flexible meshlike
macromolecule that withstands the intense internal turgor in the
cell, among other functions. The integrity of the PG layer is of the
utmost importance to bacteria, which must ensure that incorporation
of new PG strands and remodelling of the existing ones is timely
coordinated with the progression of the cell cycle. Despite its clinical
relevance, many fundamental biological processes in S. aureus remain
to be elucidated.(...)".
20
Lobo, Ricardo André Santos. "Role of DUF1727 domain in the amidation of peptidoglycan of Staphylococcus Aureus." Master's thesis, 2014. http://hdl.handle.net/10451/15979.
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Gonçalves, Rita de Sá Martins Pinto. "Study of in vivo interactions between penicillin-binding proteins of Staphylococcus aureus." Master's thesis, 2015. http://hdl.handle.net/10362/16342.
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Staphylococcus aureus (S. aureus) is a major human pathogen that has acquired resistance to practically all classes of β-lactam antibiotics, being responsible of Multidrug resistant S. aureus (MRSA) associated infections both in healthcare (HA-MRSA) and community settings (CA-MRSA). The emergence of laboratory strains with high-resistance (VRSA) to the last resort antibiotic, vancomycin, is a warning of what is to come in clinical strains. Penicillin binding proteins (PBPs) target β-lactams and are responsible for catalyzing the last steps of synthesis of the main component of cell wall, peptidoglycan. As in Escherichia coli, it is suggested that S. aureus uses a multi-protein complex that carries out cell wall synthesis. In the presence of β-lactams, PBP2A and PBP2 perform a joint action to build the cell wall and allow cell survival. Likewise, PBP2 cooperates with PBP4 in cell wall cross-linking. However, an actual interaction between PBP2 and PBP4 and the location of such interaction has not yet been determined. Therefore, investigation of the existence of a PBP2-PBP4 interaction and its location(s) in vivo is of great interest, as it should provide new insights into the function of the cell wall synthesis machinery in S. aureus. The aim of this work was to develop Split-GFPP7 system to determine interactions between PBP2 and PBP4. GFPP7 was split in a strategic site and fused to proteins of interest. When each GFPP7 fragment, fused to proteins, was expressed alone in staphylococcal cells, no fluorescence was detectable. When GFPP7 fragments fused to different peptidoglycan synthesis (PBP2 and PBP4) or cell division (FtsZ and EzrA) proteins were co-expressed together, fluorescent fusions were localized to the septum. However, further analysis revealed that this positive result is mediated by GFPP7 self-association. We then interpret the results in light of such event and provide insights into ways of improving this system.
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Marques, Patrícia Costinha. "The role of PGN hydrolases in the ability of Staphylococcus aureus to evade the host innate immune system." Master's thesis, 2017. http://hdl.handle.net/10362/31308.
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Staphylococcus aureus is an important microorganism that can be found on the skin and mucous membranes of the human body. Despite its ability to colonize the human host, invasion of this pathogen into the host tissue can lead to severe health conditions. As current antibiotics become less effective in the combat to this pathogen, it becomes urgent to develop new strategies of treatment.
Peptidoglycan is present in gram-negative and gram-positive bacteria alike, as a fundamental molecule for cell structure. It is a telltale molecule that betrays the presence of the bacteria when recognized by host innate immune receptors such as the PGRP proteins.
In order to avoid detection, S. aureus uses different strategies to circumvent recognition of the PGN at its surface. It has been shown that Atl, a major autolysin of S. aureus, is able to trim the outermost fragments of peptidoglycan in order to prevent the binding of PGRPs.
This project focused in studying the protein SAOUHSC_00671 from S. aureus NCTC 8324-5 strain, which belongs to the same protein family as SleI, a PGN hydrolase capable of trimming PGN fragments at the staphylococcal division septum. This project aimed purify the SAOUHSC_00671 protein and construct knock-out S. aureus mutants, which lack the coding sequence for SAOUHSC_00671.
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Vieira, Diana Maria Patacas Viegas. "Crystallographic studies of proteins involved in the mRNA localization mechanisms in Drosophila melanogaster and amidation of the peptidoglycan residues in Staphylococcus aureus." Doctoral thesis, 2014. http://hdl.handle.net/10362/14632.
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Part of the work described in this chapter, was the subject of the following publication:
D. Vieira, T. a. Figueiredo, A. Verma, R. G. Sobral, A. M. Ludovice, H. de Lencastre, and J. Trincao, “Purification, crystallization and preliminary X-ray diffraction analysis of GatD, a glutamine amidotransferase-like protein from Staphylococcus aureus peptidoglycan,” Acta Crystallogr. Sect. F Struct. Biol. Commun., vol. 70, no. 5, pp. 1–4, Apr. 2014.Fundação para a Ciência e a Tecnologia (FCT) - Bolsa de Doutoramento individual SFRH/BD/62415/2009, e projecto PTDC/BIA-PRO/80486/2006
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Huang, Chia-Ying, and 黃佳瑩. "Crystal structure of Staphylococcus aureus membrane-bound transglycosylase in complex with a lipid II analog and elucidation of the mechanism of peptidoglycan synthesis." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/05338663118907174645.
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博士國立陽明大學
微生物及免疫學研究所
100
Bacterial transpeptidase and transglycosylase on the cell surface are essential for cell wall synthesis and many antibiotics have been developed to target the transpeptidase, but the problem of antibiotic resistance has arisen and caused a major threat in bacterial infection. The transglycosylase has been considered to be another excellent target, but no antibiotics have been developed to target this enzyme. In this study, we first characterize the function of the transmembrane helix and the UvrB domain 2 homolog domain by complementary activity assay and isothermal titration calorimetry. Results show that both are crucial for the transglycosylase activity. Then, we determined the crystal structure of the Staphylococcus aureus membrane-bound transglycosylase, monofunctional glycosyltransferase (MGT), in complex with a lipid II analog to 2.3 angstrom resolution. Results showed that the lipid II-contacting residues are not only conserved in both wild type and drug-resistant bacteria, but also significant in enzymatic activity. Mechanistically, we proposed that K140 and R148 in the glycosyl donor site, instead of the previously proposed E156, are used to stabilize the pyrophosphate-leaving group of lipid II and E100 in the glycosyl acceptor site acts as general base for the 4-OH of GlcNAc to facilitate the transglycosylation reaction. This mechanism, further supported by mutagenesis study and the structure of MGT in complex with moenomycin in the glycosyl donor site, provides a new direction for antibacterial drugs design. Moreover, with the comprehensive crystal structures of S. aureus MGT complex and well characterization of transmembrane helix, we propose a new mechanism for the peptidolgycan synthesis.
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Portela, Raquel Pereira. "New studies in the resistance to β-lactams and in cell wall damage survival in Staphylococcus aureus: an integrated approach." Doctoral thesis, 2019. http://hdl.handle.net/10362/91350.
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