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Jang H, Do H, Kim CM, Kim GE, Lee JH, Park HH. Molecular basis of dimerization of lytic transglycosylase revealed by the crystal structure of MltA from Acinetobacter baumannii. IUCRJ 2021; 8:921-930. [PMID: 34804545 PMCID: PMC8562663 DOI: 10.1107/s2052252521008666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Accepted: 08/18/2021] [Indexed: 06/13/2023]
Abstract
Peptidoglycan digestion by murein-degrading enzymes is a critical process in bacterial cell growth and/or cell division. The membrane-bound lytic murein transglycosylase A (MltA) is a murein-degrading enzyme; it catalyzes the cleavage of the β-1,4-glycosidic linkage between N-acetylmuramic acid and N-acetylglucosamine in peptidoglycans. Although substrate recognition and cleavage by MltA have been examined by previous structural and mutagenesis studies, the overall mechanism of MltA in conjunction with other functionally related molecules on the outer membrane of bacterial cells for peptidoglycan degradation has remained elusive. In this study, the crystal structure of MltA from the virulent human pathogen Acinetobacter baumannii is characterized and presented. The study indicated that MltA from A. baumannii forms homodimers via an extra domain which is specific to this species. Furthermore, the working mechanism of MltA with various functionally related proteins on the bacterial outer membrane was modeled based on the structural and biochemical analysis.
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Affiliation(s)
- Hyunseok Jang
- College of Pharmacy, Chung-Ang University, Seoul 06974, Republic of Korea
- Department of Global Innovative Drugs, Graduate School of Chung-Ang University, Seoul 06974, Republic of Korea
| | - Hackwon Do
- Unit of Research for Practical Application, Korea Polar Research Institute, Incheon 21990, Republic of Korea
- Department of Polar Sciences, University of Science and Technology, Incheon 21990, Republic of Korea
| | - Chang Min Kim
- Department of Global Innovative Drugs, Graduate School of Chung-Ang University, Seoul 06974, Republic of Korea
| | - Gi Eob Kim
- College of Pharmacy, Chung-Ang University, Seoul 06974, Republic of Korea
- Department of Global Innovative Drugs, Graduate School of Chung-Ang University, Seoul 06974, Republic of Korea
| | - Jun Hyuck Lee
- Unit of Research for Practical Application, Korea Polar Research Institute, Incheon 21990, Republic of Korea
- Department of Polar Sciences, University of Science and Technology, Incheon 21990, Republic of Korea
| | - Hyun Ho Park
- College of Pharmacy, Chung-Ang University, Seoul 06974, Republic of Korea
- Department of Global Innovative Drugs, Graduate School of Chung-Ang University, Seoul 06974, Republic of Korea
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2
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Weaver AI, Jiménez-Ruiz V, Tallavajhala SR, Ransegnola BP, Wong KQ, Dörr T. Lytic transglycosylases RlpA and MltC assist in Vibrio cholerae daughter cell separation. Mol Microbiol 2019; 112:1100-1115. [PMID: 31286580 DOI: 10.1111/mmi.14349] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/04/2019] [Indexed: 12/21/2022]
Abstract
The cell wall is a crucial structural feature in the vast majority of bacteria and comprises a covalently closed network of peptidoglycan (PG) strands. While PG synthesis is important for survival under many conditions, the cell wall is also a dynamic structure, undergoing degradation and remodeling by 'autolysins', enzymes that break down PG. Cell division, for example, requires extensive PG remodeling, especially during separation of daughter cells, which depends heavily upon the activity of amidases. However, in Vibrio cholerae, we demonstrate that amidase activity alone is insufficient for daughter cell separation and that lytic transglycosylases RlpA and MltC both contribute to this process. MltC and RlpA both localize to the septum and are functionally redundant under normal laboratory conditions; however, only RlpA can support normal cell separation in low-salt media. The division-specific activity of lytic transglycosylases has implications for the local structure of septal PG, suggesting that there may be glycan bridges between daughter cells that cannot be resolved by amidases. We propose that lytic transglycosylases at the septum cleave PG strands that are crosslinked beyond the reach of the highly regulated activity of the amidase and clear PG debris that may block the completion of outer membrane invagination.
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Affiliation(s)
- Anna I Weaver
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, 14853, USA.,Department of Microbiology, Cornell University, Ithaca, NY, 14853, USA
| | - Valeria Jiménez-Ruiz
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Srikar R Tallavajhala
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Brett P Ransegnola
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Kimberly Q Wong
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Tobias Dörr
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, 14853, USA.,Department of Microbiology, Cornell University, Ithaca, NY, 14853, USA.,Cornell Institute of Host-Microbe Interactions and Disease, Cornell University, Ithaca, NY, 14853, USA
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3
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Jenkins CH, Wallis R, Allcock N, Barnes KB, Richards MI, Auty JM, Galyov EE, Harding SV, Mukamolova GV. The lytic transglycosylase, LtgG, controls cell morphology and virulence in Burkholderia pseudomallei. Sci Rep 2019; 9:11060. [PMID: 31363151 PMCID: PMC6667503 DOI: 10.1038/s41598-019-47483-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 07/15/2019] [Indexed: 02/07/2023] Open
Abstract
Burkholderia pseudomallei is the causative agent of the tropical disease melioidosis. Its genome encodes an arsenal of virulence factors that allow it, when required, to switch from a soil dwelling bacterium to a deadly intracellular pathogen. With a high intrinsic resistance to antibiotics and the ability to overcome challenges from the host immune system, there is an increasing requirement for new antibiotics and a greater understanding into the molecular mechanisms of B. pseudomallei virulence and dormancy. The peptidoglycan remodeling enzymes, lytic transglycosylases (Ltgs) are potential targets for such new antibiotics. Ltgs cleave the glycosidic bonds within bacterial peptidoglycan allowing for the insertion of peptidoglycan precursors during cell growth and division, and cell membrane spanning structures such as flagella and secretion systems. Using bioinformatic analysis we have identified 8 putative Ltgs in B. pseudomallei K96243. We aimed to investigate one of these Ltgs, LtgG (BPSL3046) through the generation of deletion mutants and biochemical analysis. We have shown that LtgG is a key contributor to cellular morphology, division, motility and virulence in BALB/c mice. We have determined the crystal structure of LtgG and have identified various amino acids likely to be important in peptidoglycan binding and catalytic activity. Recombinant protein assays and complementation studies using LtgG containing a site directed mutation in aspartate 343, confirmed the essentiality of this amino acid in the function of LtgG.
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Affiliation(s)
- Christopher H Jenkins
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, UK.
- Defence Science and Technology Laboratory, Chemical, Biological and Radiological Division, Porton Down, Salisbury, Wiltshire, UK.
| | - Russell Wallis
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, UK
- The Leicester Institute of Structural and Chemical Biology, Henry Wellcome Building, University of Leicester, Leicester, UK
| | - Natalie Allcock
- Electron Microscopy Facility, Core Biotechnology Services, University of Leicester, Leicester, UK
| | - Kay B Barnes
- Defence Science and Technology Laboratory, Chemical, Biological and Radiological Division, Porton Down, Salisbury, Wiltshire, UK
| | - Mark I Richards
- Defence Science and Technology Laboratory, Chemical, Biological and Radiological Division, Porton Down, Salisbury, Wiltshire, UK
| | - Joss M Auty
- Department of Respiratory Sciences, University of Leicester, Leicester, UK
| | - Edouard E Galyov
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, UK
- Department of Genetics and Genome Biology, University of Leicester, Leicester, UK
| | - Sarah V Harding
- Defence Science and Technology Laboratory, Chemical, Biological and Radiological Division, Porton Down, Salisbury, Wiltshire, UK
- Department of Respiratory Sciences, University of Leicester, Leicester, UK
| | - Galina V Mukamolova
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, UK.
- Department of Respiratory Sciences, University of Leicester, Leicester, UK.
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Gonococcal MtrE and its surface-expressed Loop 2 are immunogenic and elicit bactericidal antibodies. J Infect 2018; 77:191-204. [PMID: 29902495 DOI: 10.1016/j.jinf.2018.06.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2018] [Revised: 05/29/2018] [Accepted: 06/04/2018] [Indexed: 11/23/2022]
Abstract
OBJECTIVES The rise in multidrug resistant Neisseria gonorrhoeae poses a threat to healthcare, while the development of an effective vaccine has remained elusive due to antigenic and phase variability of surface-expressed proteins. In the current study, we identified a fully conserved surface expressed protein and characterized its suitability as a vaccine antigen. METHODS An in silico approach was used to predict surface-expressed proteins and analyze sequence conservation and phase variability. The most conserved protein and its surface-exposed Loop 2, which was displayed as both a structural and linear epitope on the oligomerization domain of C4b binding protein, were used to immunize mice. Immunogenicity was subsequently analyzed by determination of antibody titers and serum bactericidal activity. RESULTS MtrE was identified as one of the most conserved surface-expressed proteins. Furthermore, MtrE and both Loop 2-containing fusion proteins elicited high protein-specific antibody titers and particularly the two Loop 2 fusion proteins showed high anti-Loop 2 titers. In addition, antibodies raised against all three proteins were able to recognize MtrE expressed on the surface of N. gonorrhoeae and showed high MtrE-dependent bactericidal activity. CONCLUSIONS Our results show that MtrE and Loop 2 are promising novel conserved surface-expressed antigens for vaccine development against N. gonorrhoeae.
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Williams AH, Wheeler R, Rateau L, Malosse C, Chamot-Rooke J, Haouz A, Taha MK, Boneca IG. A step-by-step in crystallo guide to bond cleavage and 1,6-anhydro-sugar product synthesis by a peptidoglycan-degrading lytic transglycosylase. J Biol Chem 2018; 293:6000-6010. [PMID: 29483188 DOI: 10.1074/jbc.ra117.001095] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Revised: 02/12/2018] [Indexed: 01/13/2023] Open
Abstract
Lytic transglycosylases (LTs) are a class of enzymes important for the recycling and metabolism of peptidoglycan (PG). LTs cleave the β-1,4-glycosidic bond between N-acetylmuramic acid (MurNAc) and GlcNAc in the PG glycan strand, resulting in the concomitant formation of 1,6-anhydro-N-acetylmuramic acid and GlcNAc. No LTs reported to date have utilized chitins as substrates, despite the fact that chitins are GlcNAc polymers linked via β-1,4-glycosidic bonds, which are the known site of chemical activity for LTs. Here, we demonstrate enzymatically that LtgA, a non-canonical, substrate-permissive LT from Neisseria meningitidis utilizes chitopentaose ((GlcNAc)5) as a substrate to produce three newly identified sugars: 1,6-anhydro-chitobiose, 1,6-anhydro-chitotriose, and 1,6-anhydro-chitotetraose. Although LTs have been widely studied, their complex reactions have not previously been visualized in the crystalline state because macromolecular PG is insoluble. Here, we visualized the cleavage of the glycosidic bond and the liberation of GlcNAc-derived residues by LtgA, followed by the synthesis of atypical 1,6-anhydro-GlcNAc derivatives. In addition to the newly identified anhydro-chitin products, we identified trapped intermediates, unpredicted substrate rearrangements, sugar distortions, and a conserved crystallographic water molecule bound to the catalytic glutamate of a high-resolution native LT. This study enabled us to propose a revised alternative mechanism for LtgA that could also be applicable to other LTs. Our work contributes to the understanding of the mechanisms of LTs in bacterial cell wall biology.
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Affiliation(s)
- Allison H Williams
- From the Institut Pasteur, Département de Microbiologie, Unité Biologie et Génétique de la Paroi Bactérienne, 75015 Paris, France, .,INSERM, 75015 Paris, France
| | - Richard Wheeler
- From the Institut Pasteur, Département de Microbiologie, Unité Biologie et Génétique de la Paroi Bactérienne, 75015 Paris, France.,INSERM, 75015 Paris, France.,the Gustave Roussy Comprehensive Cancer Center, Tumour Immunology and Immunotherapy, F-94805 Villejuif, France
| | - Lesly Rateau
- From the Institut Pasteur, Département de Microbiologie, Unité Biologie et Génétique de la Paroi Bactérienne, 75015 Paris, France.,INSERM, 75015 Paris, France
| | - Christian Malosse
- the Institut Pasteur, CNRS USR 2000, Unité des Spectrométrie de Masse Structurale et Proteomique, 75015 Paris, France
| | - Julia Chamot-Rooke
- the Institut Pasteur, CNRS USR 2000, Unité des Spectrométrie de Masse Structurale et Proteomique, 75015 Paris, France
| | - Ahmed Haouz
- the Institut Pasteur, Plate-forme de Cristallographie, CNRS-UMR3528, 75724 Paris, France, and
| | - Muhamed-Kheir Taha
- the Institut Pasteur, Département d'Infection et Epidémiologie, Unité des Infection Bactériennes Invasives, 75015 Paris, France
| | - Ivo Gomperts Boneca
- From the Institut Pasteur, Département de Microbiologie, Unité Biologie et Génétique de la Paroi Bactérienne, 75015 Paris, France, .,INSERM, 75015 Paris, France
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6
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Dik DA, Marous DR, Fisher JF, Mobashery S. Lytic transglycosylases: concinnity in concision of the bacterial cell wall. Crit Rev Biochem Mol Biol 2017. [PMID: 28644060 DOI: 10.1080/10409238.2017.1337705] [Citation(s) in RCA: 100] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The lytic transglycosylases (LTs) are bacterial enzymes that catalyze the non-hydrolytic cleavage of the peptidoglycan structures of the bacterial cell wall. They are not catalysts of glycan synthesis as might be surmised from their name. Notwithstanding the seemingly mundane reaction catalyzed by the LTs, their lytic reactions serve bacteria for a series of astonishingly diverse purposes. These purposes include cell-wall synthesis, remodeling, and degradation; for the detection of cell-wall-acting antibiotics; for the expression of the mechanism of cell-wall-acting antibiotics; for the insertion of secretion systems and flagellar assemblies into the cell wall; as a virulence mechanism during infection by certain Gram-negative bacteria; and in the sporulation and germination of Gram-positive spores. Significant advances in the mechanistic understanding of each of these processes have coincided with the successive discovery of new LTs structures. In this review, we provide a systematic perspective on what is known on the structure-function correlations for the LTs, while simultaneously identifying numerous opportunities for the future study of these enigmatic enzymes.
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Affiliation(s)
- David A Dik
- a Department of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , IN , USA
| | - Daniel R Marous
- a Department of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , IN , USA
| | - Jed F Fisher
- a Department of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , IN , USA
| | - Shahriar Mobashery
- a Department of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , IN , USA
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7
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Herlihey FA, Clarke AJ. Controlling Autolysis During Flagella Insertion in Gram-Negative Bacteria. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 925:41-56. [PMID: 27722959 DOI: 10.1007/5584_2016_52] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The flagellum is an important macromolecular machine for many pathogenic bacteria. It is a hetero-oligomeric structure comprised of three major sub-structures: basal body, hook and thin helical filament. An important step during flagellum assembly is the localized and controlled degradation of the peptidoglycan sacculus to allow for the insertion of the rod as well as to facilitate anchoring for proper motor function. The peptidoglycan lysis events require specialized lytic enzymes, β-N-acetylglucosaminidases and lytic transglycosylases, which differ in flagellated proteobacteria. Due to their autolytic activity, these enzymes need to be controlled in order to prevent cellular lysis. This review summarizes are current understanding of the peptidoglycan lysis events required for flagellum assembly and motility with a main focus on Gram-negative bacteria.
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Affiliation(s)
- Francesca A Herlihey
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, N1G2W1, Canada
| | - Anthony J Clarke
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, N1G2W1, Canada.
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8
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Lamers RP, Nguyen UT, Nguyen Y, Buensuceso RNC, Burrows LL. Loss of membrane-bound lytic transglycosylases increases outer membrane permeability and β-lactam sensitivity in Pseudomonas aeruginosa. Microbiologyopen 2015; 4:879-95. [PMID: 26374494 PMCID: PMC4694138 DOI: 10.1002/mbo3.286] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Revised: 08/04/2015] [Accepted: 08/10/2015] [Indexed: 11/25/2022] Open
Abstract
The opportunistic pathogen Pseudomonas aeruginosa is a leading cause of nosocomial infections. Its relatively impermeable outer membrane (OM) limits antibiotic entry, and a chromosomally encoded AmpC β‐lactamase inactivates β‐lactam antibiotics. AmpC expression is linked to peptidoglycan (PG) recycling, and soluble (sLT) or membrane‐bound (mLT) lytic transglycosylases are responsible for generating the anhydromuropeptides that induce AmpC expression. Thus, inhibition of LT activity could reduce AmpC‐mediated β‐lactam resistance in P. aeruginosa. Here, we characterized single and combination LT mutants. Strains lacking SltB1 or MltB had increased β‐lactam minimum inhibitory concentrations (MICs) compared to wild type, while only loss of Slt decreased MICs. An sltB1 mltB double mutant had elevated β‐lactam MICs compared to either the sltB1 or mltB single mutants (96 vs. 32 μg/mL cefotaxime), without changes to AmpC levels. Time–kill assays with β‐lactams suggested that increased MIC correlated with a slower rate of autolysis in the sltB1 mltB mutant – an antisuicide phenotype. Strains lacking multiple mLTs were more sensitive to β‐lactams and up to 16‐fold more sensitive to vancomycin, normally incapable of crossing the OM. Multi‐mLT mutants were also sensitive to bile salts and osmotic stress, and were hyperbiofilm formers, all phenotypes consistent with cell envelope compromise. Complementation with genes encoding inactive forms of the enzymes – or alternatively, overexpression of Braun's lipoprotein – reversed the mutants' cell envelope damage phenotypes, suggesting that mLTs help to stabilize the OM. We conclude that P. aeruginosa mLTs contribute physically to cell envelope stability, and that Slt is the preferred target for future development of LT inhibitors that could synergize with β‐lactams.
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Affiliation(s)
- Ryan P Lamers
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
| | - Uyen T Nguyen
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
| | - Ylan Nguyen
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
| | - Ryan N C Buensuceso
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
| | - Lori L Burrows
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
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9
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Quay DHX, Cole AR, Cryar A, Thalassinos K, Williams MA, Bhakta S, Keep NH. Structure of the stationary phase survival protein YuiC from B.subtilis. BMC STRUCTURAL BIOLOGY 2015; 15:12. [PMID: 26163297 PMCID: PMC4499186 DOI: 10.1186/s12900-015-0039-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 07/02/2015] [Indexed: 11/23/2022]
Abstract
Background Stationary phase survival proteins (Sps) were found in Firmicutes as having analogous domain compositions, and in some cases genome context, as the resuscitation promoting factors of Actinobacteria, but with a different putative peptidoglycan cleaving domain. Results The first structure of a Firmicute Sps protein YuiC from B. subtilis, is found to be a stripped down version of the cell-wall peptidoglycan hydrolase MltA. The YuiC structures are of a domain swapped dimer, although some monomer is also found in solution. The protein crystallised in the presence of pentasaccharide shows a 1,6-anhydrodisaccharide sugar product, indicating that YuiC cleaves the sugar backbone to form an anhydro product at least on lengthy incubation during crystallisation. Conclusions The structural simplification of MltA in Sps proteins is analogous to that of the resuscitation promoting factor domains of Actinobacteria, which are stripped down versions of lysozyme and soluble lytic transglycosylase proteins. Electronic supplementary material The online version of this article (doi:10.1186/s12900-015-0039-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Doris H X Quay
- Institute for Structural and Molecular Biology, Crystallography, Department of Biological Sciences, Birkbeck University of London, Malet Street, London, WC1E 7HX, UK.
| | - Ambrose R Cole
- Institute for Structural and Molecular Biology, Crystallography, Department of Biological Sciences, Birkbeck University of London, Malet Street, London, WC1E 7HX, UK.
| | - Adam Cryar
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, Gower Street, London, WC1E 6BT, UK.
| | - Konstantinos Thalassinos
- Institute for Structural and Molecular Biology, Crystallography, Department of Biological Sciences, Birkbeck University of London, Malet Street, London, WC1E 7HX, UK. .,Institute of Structural and Molecular Biology, Division of Biosciences, University College London, Gower Street, London, WC1E 6BT, UK.
| | - Mark A Williams
- Institute for Structural and Molecular Biology, Crystallography, Department of Biological Sciences, Birkbeck University of London, Malet Street, London, WC1E 7HX, UK.
| | - Sanjib Bhakta
- Institute for Structural and Molecular Biology, Crystallography, Department of Biological Sciences, Birkbeck University of London, Malet Street, London, WC1E 7HX, UK.
| | - Nicholas H Keep
- Institute for Structural and Molecular Biology, Crystallography, Department of Biological Sciences, Birkbeck University of London, Malet Street, London, WC1E 7HX, UK.
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Jorgenson MA, Chen Y, Yahashiri A, Popham DL, Weiss DS. The bacterial septal ring protein RlpA is a lytic transglycosylase that contributes to rod shape and daughter cell separation in Pseudomonas aeruginosa. Mol Microbiol 2014; 93:113-28. [PMID: 24806796 DOI: 10.1111/mmi.12643] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/06/2014] [Indexed: 11/28/2022]
Abstract
Rare lipoprotein A (RlpA) is a widely conserved outer membrane protein of unknown function that has previously only been studied in Escherichia coli, where it localizes to the septal ring and scattered foci along the lateral wall, but mutants have no phenotypic change. Here we show rlpA mutants of Pseudomonas aeruginosa form chains of short, fat cells when grown in low osmotic strength media. These morphological defects indicate RlpA is needed for efficient separation of daughter cells and maintenance of rod shape. Analysis of peptidoglycan sacculi from an rlpA deletion mutant revealed increased tetra and hexasaccharides that lack stem peptides (hereafter called 'naked glycans'). Incubation of these sacculi with purified RlpA resulted in release of naked glycans containing 1,6-anhydro N-acetylmuramic acid ends. RlpA did not degrade sacculi from wild-type cells unless the sacculi were subjected to a limited digestion with an amidase to remove some of the stem peptides. Thus, RlpA is a lytic transglycosylase with a strong preference for naked glycan strands. We propose that RlpA activity is regulated in vivo by substrate availability, and that amidases and RlpA work in tandem to degrade peptidoglycan in the division septum and lateral wall.
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Affiliation(s)
- Matthew A Jorgenson
- Department of Microbiology, Carver College of Medicine, The University of Iowa, Iowa City, IA, 52242, USA
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11
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Moynie L, Schnell R, McMahon SA, Sandalova T, Boulkerou WA, Schmidberger JW, Alphey M, Cukier C, Duthie F, Kopec J, Liu H, Jacewicz A, Hunter WN, Naismith JH, Schneider G. The AEROPATH project targeting Pseudomonas aeruginosa: crystallographic studies for assessment of potential targets in early-stage drug discovery. Acta Crystallogr Sect F Struct Biol Cryst Commun 2013; 69:25-34. [PMID: 23295481 PMCID: PMC3539698 DOI: 10.1107/s1744309112044739] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Accepted: 10/29/2012] [Indexed: 12/25/2022]
Abstract
Bacterial infections are increasingly difficult to treat owing to the spread of antibiotic resistance. A major concern is Gram-negative bacteria, for which the discovery of new antimicrobial drugs has been particularly scarce. In an effort to accelerate early steps in drug discovery, the EU-funded AEROPATH project aims to identify novel targets in the opportunistic pathogen Pseudomonas aeruginosa by applying a multidisciplinary approach encompassing target validation, structural characterization, assay development and hit identification from small-molecule libraries. Here, the strategies used for target selection are described and progress in protein production and structure analysis is reported. Of the 102 selected targets, 84 could be produced in soluble form and the de novo structures of 39 proteins have been determined. The crystal structures of eight of these targets, ranging from hypothetical unknown proteins to metabolic enzymes from different functional classes (PA1645, PA1648, PA2169, PA3770, PA4098, PA4485, PA4992 and PA5259), are reported here. The structural information is expected to provide a firm basis for the improvement of hit compounds identified from fragment-based and high-throughput screening campaigns.
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Affiliation(s)
- Lucille Moynie
- Biomedical Sciences Research Complex, University of St Andrews, St Andrews KY16 9ST, Scotland
| | - Robert Schnell
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Stephen A. McMahon
- Biomedical Sciences Research Complex, University of St Andrews, St Andrews KY16 9ST, Scotland
| | - Tatyana Sandalova
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | | | - Jason W. Schmidberger
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Magnus Alphey
- Biomedical Sciences Research Complex, University of St Andrews, St Andrews KY16 9ST, Scotland
| | - Cyprian Cukier
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Fraser Duthie
- Biomedical Sciences Research Complex, University of St Andrews, St Andrews KY16 9ST, Scotland
| | - Jolanta Kopec
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Huanting Liu
- Biomedical Sciences Research Complex, University of St Andrews, St Andrews KY16 9ST, Scotland
| | - Agata Jacewicz
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - William N. Hunter
- Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland
| | - James H. Naismith
- Biomedical Sciences Research Complex, University of St Andrews, St Andrews KY16 9ST, Scotland
| | - Gunter Schneider
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden
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Abstract
Many Gram-negative and Gram-positive bacteria recycle a significant proportion of the peptidoglycan components of their cell walls during their growth and septation. In many--and quite possibly all--bacteria, the peptidoglycan fragments are recovered and recycled. Although cell-wall recycling is beneficial for the recovery of resources, it also serves as a mechanism to detect cell-wall-targeting antibiotics and to regulate resistance mechanisms. In several Gram-negative pathogens, anhydro-MurNAc-peptide cell-wall fragments regulate AmpC β-lactamase induction. In some Gram-positive organisms, short peptides derived from the cell wall regulate the induction of both β-lactamase and β-lactam-resistant penicillin-binding proteins. The involvement of peptidoglycan recycling with resistance regulation suggests that inhibitors of the enzymes involved in the recycling might synergize with cell-wall-targeted antibiotics. Indeed, such inhibitors improve the potency of β-lactams in vitro against inducible AmpC β-lactamase-producing bacteria. We describe the key steps of cell-wall remodeling and recycling, the regulation of resistance mechanisms by cell-wall recycling, and recent advances toward the discovery of cell-wall-recycling inhibitors.
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Affiliation(s)
- Jarrod W Johnson
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA
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13
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Tomberg J, Temple B, Fedarovich A, Davies C, Nicholas RA. A highly conserved interaction involving the middle residue of the SXN active-site motif is crucial for function of class B penicillin-binding proteins: mutational and computational analysis of PBP 2 from N. gonorrhoeae. Biochemistry 2012; 51:2775-84. [PMID: 22397678 PMCID: PMC3338128 DOI: 10.1021/bi2017987] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Insertion of an aspartate residue at position 345a in penicillin-binding protein 2 (PBP 2), which lowers the rate of penicillin acylation by ~6-fold, is commonly observed in penicillin-resistant strains of Neisseria gonorrhoeae. Here, we show that insertions of other amino acids also lower the penicillin acylation rate of PBP 2, but none supported growth of N. gonorrhoeae, indicating loss of essential transpeptidase activity. The Asp345a mutation likely acts by altering the interaction between its adjacent residue, Asp346, in the β2a-β2d hairpin loop and Ser363, the middle residue of the SXN active site motif. Because the adjacent aspartate creates ambiguity in the position of the insertion, we also examined if insertions at position 346a could confer decreased susceptibility to penicillin. However, only aspartate insertions were identified, indicating that only an Asp-Asp couple can confer resistance and retain transpeptidase function. The importance of the Asp346-Ser363 interaction was assessed by mutation of each residue to Ala. Although both mutants lowered the acylation rate of penicillin G by 5-fold, neither could support growth of N. gonorrhoeae, again indicating loss of transpeptidase function. Interaction between a residue in the equivalent of the β2a-β2d hairpin loop and the middle residue of the SXN motif is observed in crystal structures of other Class B PBPs, and its importance is also supported by multisequence alignments. Overall, these results suggest that this conserved interaction can be manipulated (e.g., by insertion) to lower the acylation rate by β-lactam antibiotics and increase resistance, but only if essential transpeptidase activity is preserved.
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Affiliation(s)
- Joshua Tomberg
- Department of Pharmacology University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365
| | - Brenda Temple
- Departments of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365
- Departments of R. L. Juliano Structural Bioinformatics Core Facility, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365
| | - Alena Fedarovich
- Department of Biochemistry, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Christopher Davies
- Department of Biochemistry, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Robert A. Nicholas
- Department of Pharmacology University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365
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14
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Chan YA, Hackett KT, Dillard JP. The lytic transglycosylases of Neisseria gonorrhoeae. Microb Drug Resist 2012; 18:271-9. [PMID: 22432703 DOI: 10.1089/mdr.2012.0001] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
Abstract
Neisseria gonorrhoeae encodes five lytic transglycosylases (LTs) in the core genome, and most gonococcal strains also carry the gonococcal genetic island that encodes one or two additional LTs. These peptidoglycan (PG)-degrading enzymes are required for a number of processes that are either involved in the normal growth of the bacteria or affect the pathogenesis and gene transfer aspects of this species that make N. gonorrhoeae highly inflammatory and highly genetically variable. Systematic mutagenesis determined that two LTs are involved in producing the 1,6-anhydro PG monomers that cause the death of ciliated cells in Fallopian tubes. Here, we review the information available on these enzymes and discuss their roles in bacterial growth, cell separation, autolysis, type IV secretion, and pathogenesis.
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Affiliation(s)
- Yolande A Chan
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin 53706, USA
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15
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Abstract
The review summarizes the abundant information on the 35 identified peptidoglycan (PG) hydrolases of Escherichia coli classified into 12 distinct families, including mainly glycosidases, peptidases, and amidases. An attempt is also made to critically assess their functions in PG maturation, turnover, elongation, septation, and recycling as well as in cell autolysis. There is at least one hydrolytic activity for each bond linking PG components, and most hydrolase genes were identified. Few hydrolases appear to be individually essential. The crystal structures and reaction mechanisms of certain hydrolases having defined functions were investigated. However, our knowledge of the biochemical properties of most hydrolases still remains fragmentary, and that of their cellular functions remains elusive. Owing to redundancy, PG hydrolases far outnumber the enzymes of PG biosynthesis. The presence of the two sets of enzymes acting on the PG bonds raises the question of their functional correlations. It is difficult to understand why E. coli keeps such a large set of PG hydrolases. The subtle differences in substrate specificities between the isoenzymes of each family certainly reflect a variety of as-yet-unidentified physiological functions. Their study will be a far more difficult challenge than that of the steps of the PG biosynthesis pathway.
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Affiliation(s)
- Jean van Heijenoort
- Institut de Biochimie et Biophysique Moléculaire et Cellulaire, Bat 430, Université Paris-Sud, Orsay F-91405, France.
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16
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de Oliveira AL, Gallo M, Pazzagli L, Benedetti CE, Cappugi G, Scala A, Pantera B, Spisni A, Pertinhez TA, Cicero DO. The structure of the elicitor Cerato-platanin (CP), the first member of the CP fungal protein family, reveals a double ψβ-barrel fold and carbohydrate binding. J Biol Chem 2011; 286:17560-8. [PMID: 21454637 DOI: 10.1074/jbc.m111.223644] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cerato-platanin (CP) is a secretion protein produced by the fungal pathogen Ceratocystis platani, the causal agent of the plane canker disease and the first member of the CP family. CP is considered a pathogen-associated molecular pattern because it induces various defense responses in the host, including production of phytoalexins and cell death. Although much is known about the properties of CP and related proteins as elicitors of plant defense mechanisms, its biochemical activity and host target(s) remain elusive. Here, we present the three-dimensional structure of CP. The protein, which exhibits a remarkable pH and thermal stability, has a double ψβ-barrel fold quite similar to those found in expansins, endoglucanases, and the plant defense protein barwin. Interestingly, although CP lacks lytic activity against a variety of carbohydrates, it binds oligosaccharides. We identified the CP region responsible for binding as a shallow surface located at one side of the β-barrel. Chemical shift perturbation of the protein amide protons, induced by oligo-N-acetylglucosamines of various size, showed that all the residues involved in oligosaccharide binding are conserved among the members of the CP family. Overall, the results suggest that CP might be involved in polysaccharide recognition and that the double ψβ-barrel fold is widespread in distantly related organisms, where it is often involved in host-microbe interactions.
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17
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Artola-Recolons C, Carrasco-López C, Llarrull LI, Kumarasiri M, Lastochkin E, Martínez de Ilarduya I, Meindl K, Usón I, Mobashery S, Hermoso JA. High-resolution crystal structure of MltE, an outer membrane-anchored endolytic peptidoglycan lytic transglycosylase from Escherichia coli. Biochemistry 2011; 50:2384-6. [PMID: 21341761 DOI: 10.1021/bi200085y] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The crystal structure of the first endolytic peptidoglycan lytic transglycosylase MltE from Escherichia coli is reported here. The degradative activity of this enzyme initiates the process of cell wall recycling, which is an integral event in the existence of bacteria. The structure sheds light on how MltE recognizes its substrate, the cell wall peptidoglycan. It also explains the ability of this endolytic enzyme to cleave in the middle of the peptidoglycan chains. Furthermore, the structure reveals how the enzyme is sequestered on the inner leaflet of the outer membrane.
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Affiliation(s)
- Cecilia Artola-Recolons
- Department of Crystallography and Structural Biology, Instituto de Química-Física "Rocasolano", CSIC, Serrano 119, 28006 Madrid, Spain
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18
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Artola-Recolons C, Llarrull LI, Lastochkin E, Mobashery S, Hermoso JA. Crystallization and preliminary X-ray diffraction analysis of the lytic transglycosylase MltE from Escherichia coli. Acta Crystallogr Sect F Struct Biol Cryst Commun 2011; 67:161-3. [PMID: 21206052 PMCID: PMC3080000 DOI: 10.1107/s1744309110049171] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Accepted: 11/24/2010] [Indexed: 11/10/2022]
Abstract
MltE from Escherichia coli (193 amino acids, 21,380 Da) is a lytic transglycosylase that initiates the first step of cell-wall recycling. This enzyme is responsible for the cleavage of the cell-wall peptidoglycan at the β-1,4-glycosidic bond between the N-acetylglucosamine and N-acetylmuramic acid units. At the end this reaction generates a disaccharide that is internalized and initiates the recycling process. To obtain insights into the biological functions of MltE, crystallization trials were performed and crystals of MltE protein that were suitable for X-ray diffraction analysis were obtained. The MltE protein of E. coli was crystallized using the hanging-drop vapour-diffusion method at 291 K. Crystals grew from a mixture consisting of 28% polyethylene glycol 4000, 0.1 M Tris pH 8.4 and 0.2 M magnesium chloride. Further optimization was performed using the microbatch technique. Single crystals were obtained that belonged to the orthorhombic space group C222(1), with unit-cell parameters a=123.32, b=183.93, c=35.29 Å, and diffracted to a resolution of 2.1 Å.
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Affiliation(s)
- Cecilia Artola-Recolons
- Department of Crystallography and Structural Biology, Instituto de Química-Física ‘Rocasolano’, Consejo Superior de Investigaciones Científicas, Serrano 119, Madrid 28006, Spain
| | - Leticia I. Llarrull
- Department of Chemistry and Biochemistry, Nieuwland Science Hall, Notre Dame, Indiana 46556, USA
| | - Elena Lastochkin
- Department of Chemistry and Biochemistry, Nieuwland Science Hall, Notre Dame, Indiana 46556, USA
| | - Shahriar Mobashery
- Department of Chemistry and Biochemistry, Nieuwland Science Hall, Notre Dame, Indiana 46556, USA
| | - Juan A. Hermoso
- Department of Crystallography and Structural Biology, Instituto de Química-Física ‘Rocasolano’, Consejo Superior de Investigaciones Científicas, Serrano 119, Madrid 28006, Spain
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19
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Yang Y, Li C. Transcription and genetic analyses of a putative N-acetylmuramyl-L-alanine amidase in Borrelia burgdorferi. FEMS Microbiol Lett 2008; 290:164-73. [PMID: 19025570 DOI: 10.1111/j.1574-6968.2008.01416.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
In this study, a putative N-acetylmuramyl-l-alanine amidase gene (bb0666) was identified in the genome of the Lyme disease spirochete Borrelia burgdorferi. This protein shares c. 30% identity with its counterparts from other bacteria. Reverse transcriptase-PCR analysis showed that bb0666 along with two other genes (bb0665 and bb0667) are cotranscribed with the motility and chemotaxis genes. This newly identified operon is termed as pami. Sequence and primer extension analyses showed that pami was regulated by a sigma(70)-like promoter, which is designated as P(ami). Transcriptional analysis using a gene encoding green fluorescence protein as a reporter demonstrated that P(ami) functions in both Escherichia coli and B. burgdorferi. Genetic studies showed that the Deltabb0666 mutant grows in long chains of unseparated cells, whose phenotype is similar to its counterparts in E. coli. Taken together, these results demonstrate that bb0666 is a homolog of MurNac-LAAs that contributes to the cell division of B. burgdorferi.
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Affiliation(s)
- Yu Yang
- Department of Oral Biology, State University of New York at Buffalo, NY 14214-3092, USA
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20
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Suvorov M, Lee M, Hesek D, Boggess B, Mobashery S. Lytic transglycosylase MltB of Escherichia coli and its role in recycling of peptidoglycan strands of bacterial cell wall. J Am Chem Soc 2008; 130:11878-9. [PMID: 18700763 DOI: 10.1021/ja805482b] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The cell wall is an indispensable structure for the survival of bacteria and a target for antibiotics. Peptidoglycan is the major constituent of the cell wall, which is comprised of backbone repeats of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM). A peptide stem is appended to the NAM unit, which in turn experiences cross-linking with a peptide from another peptidoglycan in the final steps of cell wall assembly. In the normal course of bacterial growth, as much as 60% of the parental cell wall is recycled, a process that is not fully understood. A polymeric cell wall is fragmented by the family of lytic transglycosylases, and certain key fragments are transported to the cytoplasm for recycling. The genes for the six known lytic transglycosylases of Escherichia coli were cloned, and the enzymes were purified in this study. It is shown that MltB is the only lytic transglycosylase to turn over a synthetic peptidoglycan fragment of two NAG-NAM repeats; hence this enzyme is likely to be the lytic transglycosylase responsible for processing of shorter peptidoglycan strands. Lytic transglycosylases have been proposed to go through an oxocarbenium species that would trap the 6-hydroxyl moiety of the glucosamine residue of muramic acid to generate the so-called 1,6-anhydromuramyl moiety. It is documented herein by characterization of the products of turnover that this process takes place to the total exclusion of the entrapment of a water molecule by the reactive intermediary oxocarbenium species. Furthermore, turnover of the E. coli sacculus (whole cell wall) by MltB was characterized. It is documented that each MltB molecule is able to process the cell wall 14000 times in the course of a single doubling time for E. coli.
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Affiliation(s)
- Maxim Suvorov
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA
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21
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Vollmer W, Joris B, Charlier P, Foster S. Bacterial peptidoglycan (murein) hydrolases. FEMS Microbiol Rev 2008; 32:259-86. [PMID: 18266855 DOI: 10.1111/j.1574-6976.2007.00099.x] [Citation(s) in RCA: 609] [Impact Index Per Article: 38.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Most bacteria have multiple peptidoglycan hydrolases capable of cleaving covalent bonds in peptidoglycan sacculi or its fragments. An overview of the different classes of peptidoglycan hydrolases and their cleavage sites is provided. The physiological functions of these enzymes include the regulation of cell wall growth, the turnover of peptidoglycan during growth, the separation of daughter cells during cell division and autolysis. Specialized hydrolases enlarge the pores in the peptidoglycan for the assembly of large trans-envelope complexes (pili, flagella, secretion systems), or they specifically cleave peptidoglycan during sporulation or spore germination. Moreover, peptidoglycan hydrolases are involved in lysis phenomena such as fratricide or developmental lysis occurring in bacterial populations. We will also review the current view on the regulation of autolysins and on the role of cytoplasm hydrolases in peptidoglycan recycling and induction of beta-lactamase.
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Affiliation(s)
- Waldemar Vollmer
- Institute for Cell and Molecular Biosciences, University of Newcastle upon Tyne, Newcastle upon Tyne, UK.
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22
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Scheurwater E, Reid CW, Clarke AJ. Lytic transglycosylases: Bacterial space-making autolysins. Int J Biochem Cell Biol 2008; 40:586-91. [PMID: 17468031 DOI: 10.1016/j.biocel.2007.03.018] [Citation(s) in RCA: 220] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2007] [Revised: 03/20/2007] [Accepted: 03/21/2007] [Indexed: 11/29/2022]
Abstract
Lytic transglycosylases are an important class of bacterial enzymes that act on peptidoglycan with the same substrate specificity as lysozyme. Unlike the latter enzymes, however, the lytic transglycosylases are not hydrolases but instead cleave the glycosidic linkage between N-actetylmuramoyl and N-acetylglucosaminyl residues with the concomitant formation of a 1,6-anydromuramoyl product. They are ubiquitous in bacteria which produce a compliment of different forms that are responsible for creating space within the peptidoglycan sacculus for its biosynthesis and recycling, cell division, and the insertion of cell-envelope spanning structures, such as flagella and secretion systems. As well, the lytic transglyosylases may have a role in pathogenesis of some bacterial species. Given their important role in bacterial cell wall metabolism, the lytic transglycosylases may present an attractive new target for the development of broad-spectrum antibiotics.
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Affiliation(s)
- Edie Scheurwater
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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23
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van Straaten KE, Barends TRM, Dijkstra BW, Thunnissen AMWH. Structure of Escherichia coli Lytic Transglycosylase MltA with Bound Chitohexaose. J Biol Chem 2007; 282:21197-205. [PMID: 17502382 DOI: 10.1074/jbc.m701818200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Crystal structures of an inactive mutant (D308A) of the lytic transglycosylase MltA from Escherichia coli have been determined in two different apo-forms, as well as in complex with the substrate analogue chitohexaose. The chitohexaose binds with all six saccharide residues in the active site groove, with an intact glycosidic bond at the bond cleavage center. Its binding induces a large reorientation of the two structural domains in MltA, narrowing the active site groove and allowing tight interactions of the oligosaccharide with residues from both domains. The structures identify residues in MltA with key roles in the binding and recognition of peptidoglycan and confirm that Asp-308 is the single catalytic residue, acting as a general acid/base. Moreover, the structures suggest that catalysis involves a high energy conformation of the scissile glycosidic linkage and that the putative oxocarbenium ion intermediate is stabilized by the dipole moment of a nearby alpha-helix.
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Affiliation(s)
- Karin E van Straaten
- Laboratory of Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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