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Som N, Reddy M. Cross-talk between phospholipid synthesis and peptidoglycan expansion by a cell wall hydrolase. Proc Natl Acad Sci U S A 2023; 120:e2300784120. [PMID: 37276399 PMCID: PMC10268279 DOI: 10.1073/pnas.2300784120] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2023] [Accepted: 05/04/2023] [Indexed: 06/07/2023] Open
Abstract
The Gram-negative bacterial cell envelope is a complex multilayered structure comprising a bilayered phospholipid (PL) membrane that surrounds the cytoplasm (inner membrane or IM) and an asymmetric outer membrane (OM) with PLs in the inner leaflet and lipopolysaccharides in the outer leaflet. Between these two layers is the periplasmic space, which contains a highly cross-linked mesh-like glycan polymer, peptidoglycan (PG). During cell expansion, coordinated synthesis of each of these components is required to maintain the integrity of the cell envelope; however, it is currently not clear how such coordination is achieved. In this study, we show that a cross-link-specific PG hydrolase couples the expansion of PG sacculus with that of PL synthesis in the Gram-negative model bacterium, Escherichia coli. We find that unregulated activity of a PG hydrolytic enzyme, MepS is detrimental for growth of E. coli during fatty acid (FA)-limiting conditions. Further genetic and biochemical analyses revealed that cellular availability of FA or PL alters the post-translational stability of MepS by modulating the proteolytic activity of a periplasmic adaptor-protease complex, NlpI-Prc toward MepS. Our results indicate that loss of OM lipid asymmetry caused by alterations in PL abundance leads to the generation of a signal to the NlpI-Prc complex for the stabilization of MepS, which subsequently cleaves the cross-links to facilitate expansion of PG. In summary, our study shows the existence of a molecular cross-talk that enables coordinated expansion of the PG sacculus with that of membrane synthesis for balanced cell-envelope biogenesis.
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Affiliation(s)
- Nilanjan Som
- Centre for Cellular and Molecular Biology, Hyderabad, 500007Telangana, India
| | - Manjula Reddy
- Centre for Cellular and Molecular Biology, Hyderabad, 500007Telangana, India
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2
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Lee WC, Jang A, Lee JY, Kim Y. Structural implication of substrate binding by peptidoglycan remodeling enzyme MepS. Biochem Biophys Res Commun 2021; 583:178-183. [PMID: 34741988 DOI: 10.1016/j.bbrc.2021.10.050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2021] [Accepted: 10/21/2021] [Indexed: 11/26/2022]
Abstract
Constant remodeling is necessary for bacterial cell growth and bacterial morphogenesis; peptidoglycan (PG) is a crucial component in this process. Murein DD-endopeptidase (MepS), initially annotated as Spr from E. coli K12, is a NlpC/P60 family endopeptidase, which cleaves the meso-diaminopimelate (DAP)-D-Ala peptide bond of PG. The Cys68, His119, His131 triad form the active site residues. MepS has autolytic activity, which is strictly regulated by a periplasmic degradation system comprising the NlpI/Prc protease complex. MepS is essential for maintaining the cell viability, and therefore, it is a potential target for developing antibiotics. This study aimed to understand the structural basis of substrate recognition and degradation. We determined the high-resolution structures of MepS, after mutating Cys68 to serine (MepS-C68S) to improve stability. We further found that citrate and L-malate molecules bind to the active site of MepS-C68S; this is in line with the recurrent observation of organic acids binding to PG endopeptidases. The presence of conserved residues on the surface revealed the potential peptide binding sites of MepS. We modelled a cross-linked peptide model of meso-DAP-D-Ala-meso-DAP, bound to the active site groove of MepS-C68S. Two conserved tyrosine residues, Tyr56 and Tyr147 appeared to be essential for the recognition of peptides. Our structural discoveries could provide insights for the design of novel antibiotics targeting MepS.
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Affiliation(s)
- Woo Cheol Lee
- Department of Bioscience and Biotechnology, Konkuk University, 120 Neungdong-ro, Seoul, 05029, Republic of Korea
| | - Ahjin Jang
- Department of Bioscience and Biotechnology, Konkuk University, 120 Neungdong-ro, Seoul, 05029, Republic of Korea
| | - Jee-Young Lee
- Molecular Design Team, New Drug Development Center, Daegu Gyeongbuk Medical Innovation Foundation (DGMIF), Daegu, 41061, Republic of Korea
| | - Yangmee Kim
- Department of Bioscience and Biotechnology, Konkuk University, 120 Neungdong-ro, Seoul, 05029, Republic of Korea.
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3
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Kim YJ, Choi BJ, Park SH, Lee HB, Son JE, Choi U, Chi WJ, Lee CR. Distinct Amino Acid Availability-Dependent Regulatory Mechanisms of MepS and MepM Levels in Escherichia coli. Front Microbiol 2021; 12:677739. [PMID: 34276609 PMCID: PMC8278236 DOI: 10.3389/fmicb.2021.677739] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 05/28/2021] [Indexed: 12/17/2022] Open
Abstract
Peptidoglycan (PG) hydrolases play important roles in various aspects of bacterial physiology, including cytokinesis, PG synthesis, quality control of PG, PG recycling, and antibiotic resistance. However, the regulatory mechanisms of their expression are poorly understood. In this study, we have uncovered novel regulatory mechanisms of the protein levels of the synthetically lethal PG endopeptidases MepS and MepM, which are involved in PG synthesis. A mutant defective for both MepS and MepM was lethal in an amino acid-rich medium, whereas it exhibited almost normal growth in a minimal medium, suggesting the expendability of MepS and MepM in a minimal medium. Protein levels of MepS and MepM dramatically decreased in the minimal medium. Although MepM was revealed as a substrate of Prc, a periplasmic protease involved in the proteolysis of MepS, only the decrease in the MepS level in the minimal medium was affected by the prc depletion. Phenotypic and biochemical analyses showed that the presence of aromatic amino acids in the medium induced the accumulation of MepS, but not MepM, while the presence of glutamate increased the level of MepM, but not MepS. Together, these results demonstrate that the protein levels of the two major PG endopeptidases are regulated in an amino acid availability-dependent manner, but their molecular mechanisms and signaling are significantly distinct.
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Affiliation(s)
- Yung Jae Kim
- Department of Biological Sciences, Myongji University, Yongin, South Korea
| | - Byoung Jun Choi
- Department of Biological Sciences, Myongji University, Yongin, South Korea
| | - Si Hyoung Park
- Department of Biological Sciences, Myongji University, Yongin, South Korea
| | - Han Byeol Lee
- Department of Biological Sciences, Myongji University, Yongin, South Korea
| | - Ji Eun Son
- Department of Biological Sciences, Myongji University, Yongin, South Korea
| | - Umji Choi
- Department of Biological Sciences, Myongji University, Yongin, South Korea
| | - Won-Jae Chi
- Biological and Genetic Resource Assessment Division, National Institute of Biological Resource, Incheon, South Korea
| | - Chang-Ro Lee
- Department of Biological Sciences, Myongji University, Yongin, South Korea
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4
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Huang WC, Hashimoto M, Shih YL, Wu CC, Lee MF, Chen YL, Wu JJ, Wang MC, Lin WH, Hong MY, Teng CH. Peptidoglycan Endopeptidase Spr of Uropathogenic Escherichia coli Contributes to Kidney Infections and Competitive Fitness During Bladder Colonization. Front Microbiol 2021; 11:586214. [PMID: 33391204 PMCID: PMC7774453 DOI: 10.3389/fmicb.2020.586214] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 11/25/2020] [Indexed: 11/27/2022] Open
Abstract
Uropathogenic Escherichia coli (UPEC) is the most common pathogen of urinary tract infections (UTIs). Antibiotic therapy is the conventional measure to manage such infections. However, the rapid emergence of antibiotic resistance has reduced the efficacy of antibiotic treatment. Given that the bacterial factors required for the full virulence of the pathogens are potential therapeutic targets, identifying such factors may facilitate the development of novel therapeutic strategies against UPEC UTIs. The peptidoglycan (PG) endopeptidase Spr (also named MepS) is required for PG biogenesis in E. coli. In the present study, we found that Spr deficiency attenuated the ability of UPEC to infect kidneys and induced a fitness defect during bladder colonization in a mouse model of UTI. Based on the liquid chromatography (LC)/mass spectrometry (MS)/MS analysis of the bacterial envelope, spr deletion changed the levels of some envelope-associated proteins, suggesting that Spr deficiency interfere with the components of the bacterial structure. Among the proteins, FliC was significantly downregulated in the spr mutant, which is resulted in reduced motility. Lack of Spr might hinder the function of the flagellar transcriptional factor FlhDC to decrease FliC expression. The motility downregulation contributed to the reduced fitness in urinary tract colonization. Additionally, spr deletion compromised the ability of UPEC to evade complement-mediated attack and to resist intracellular killing of phagocytes, consequently decreasing UPEC bloodstream survival. Spr deficiency also interfered with the UPEC morphological switch from bacillary to filamentous shapes during UTI. It is known that bacterial filamentation protects UPEC from phagocytosis by phagocytes. In conclusion, Spr deficiency was shown to compromise multiple virulence properties of UPEC, leading to attenuation of the pathogen in urinary tract colonization and bloodstream survival. These findings indicate that Spr is a potential antimicrobial target for further studies attempting to develop novel strategies in managing UPEC UTIs.
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Affiliation(s)
- Wen-Chun Huang
- Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Masayuki Hashimoto
- Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Center of Infectious Disease and Signaling Research, National Cheng Kung University, Tainan, Taiwan
| | - Yu-Ling Shih
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Chia-Ching Wu
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Department of Cell Biology and Anatomy, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Mei-Feng Lee
- Department of Biotechnology, National Kaohsiung Normal University, Kaohsiung, Taiwan
| | - Ya-Lei Chen
- Department of Biotechnology, National Kaohsiung Normal University, Kaohsiung, Taiwan
| | - Jiunn-Jong Wu
- Department of Biotechnology and Laboratory Science in Medicine, School of Biomedical Science and Engineering, National Yang Ming University, Taipei, Taiwan
| | - Ming-Cheng Wang
- Division of Nephrology, Department of Internal Medicine, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Wei-Hung Lin
- Division of Nephrology, Department of Internal Medicine, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Ming-Yuan Hong
- Department of Emergency Medicine, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Ching-Hao Teng
- Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Center of Infectious Disease and Signaling Research, National Cheng Kung University, Tainan, Taiwan
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5
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Park SH, Kim YJ, Lee HB, Seok YJ, Lee CR. Genetic Evidence for Distinct Functions of Peptidoglycan Endopeptidases in Escherichia coli. Front Microbiol 2020; 11:565767. [PMID: 33013796 PMCID: PMC7516022 DOI: 10.3389/fmicb.2020.565767] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 08/17/2020] [Indexed: 02/01/2023] Open
Abstract
Peptidoglycan (PG) is an essential component of the bacterial exoskeleton that plays a pivotal role in the maintenance of cell shape and resistance to cell lysis under high turgor pressures. The synthesis and degradation of PG must be tightly regulated during bacterial cell elongation and division. Unlike enzymes involved in PG synthesis, PG hydrolases show high redundancy in many bacteria including Escherichia coli. In this study, we showed that PG endopeptidases have distinct roles in cell growth and division. Phenotypic analysis of mutants lacking one of seven PG endopeptidases identified a MepM-specific phenotype, salt sensitivity, and a MepS-specific phenotype, EDTA sensitivity. Complementation test in each phenotype showed that the phenotype of the mepM mutant was restored only by MepM, whereas the phenotype of the mepS mutant was restored by MepS or by overexpression of MepH, PbpG, or MepM. These distinct phenotypes depend on both the specific localizations and specific domains of MepM and MepS. Finally, using the identified phenotypes, we revealed that MepM and MepH were genetically associated with both penicillin-binding protein 1a (PBP1a) and PBP1b, whereas MepS and PbpG were genetically associated with only PBP1b. Notably, a defect in PBP1a or PBP1b phenocopied the mepM mutant, suggesting the importance of MepM on PG synthesis. Therefore, our results indicate that each PG endopeptidase plays a distinct role in cell growth and division, depending on its distinct domains and cellular localizations.
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Affiliation(s)
- Si Hyoung Park
- Department of Biological Sciences and Bioinformatics, Myongji University, Yongin, South Korea
| | - Yung Jae Kim
- Department of Biological Sciences and Bioinformatics, Myongji University, Yongin, South Korea
| | - Han Byeol Lee
- Department of Biological Sciences and Bioinformatics, Myongji University, Yongin, South Korea
| | - Yeong-Jae Seok
- Department of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul, South Korea
| | - Chang-Ro Lee
- Department of Biological Sciences and Bioinformatics, Myongji University, Yongin, South Korea
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6
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Hsu PC, Chen CS, Wang S, Hashimoto M, Huang WC, Teng CH. Identification of MltG as a Prc Protease Substrate Whose Dysregulation Contributes to the Conditional Growth Defect of Prc-Deficient Escherichia coli. Front Microbiol 2020; 11:2000. [PMID: 32973722 PMCID: PMC7481392 DOI: 10.3389/fmicb.2020.02000] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 07/28/2020] [Indexed: 11/13/2022] Open
Abstract
Microbial proteases play pivotal roles in many aspects of bacterial physiological processes. Because a protease exerts its biological function by proteolytically regulating its substrates, the identification and characterization of the physiological substrates of a protease advance our understanding of the biological roles of the protease. Prc (also named Tsp) is an Escherichia coli periplasmic protease thought to be indispensable for E. coli to survive under low osmolality at 42°C. The accumulation of the Prc substrate MepS due to Prc deficiency contributes to the conditional growth defect. Because preventing MepS accumulation only partially restored the growth of Prc-deficient E. coli, we hypothesized that other unidentified Prc substrates intracellularly accumulate due to Prc deficiency and contribute to the conditional growth defect. To identify previously undiscovered substrates, 85 E. coli proteins able to physically interact with Prc were identified using E. coli proteome arrays. Ten proteins were shown to be cleavable by Prc in vitro. Among these candidates, MltG was able to interact with Prc in E. coli. Prc regulated the intracellular level of MltG, indicating that MltG is a physiological substrate of Prc. Prc deficiency induced the accumulation of MltG in the bacteria. Blocking MltG accumulation by deleting mltG partially restored the growth of Prc-deficient E. coli. In addition, Prc-deficient E. coli with blocked MltG and MepS expression exhibited higher growth levels than those with only the MltG or MepS expression blocked under low osmolality at 42°C, suggesting that these accumulated substrates additively contributed to the conditional growth defect. MltG is a lytic transglycosylase involved in the biogenesis of peptidoglycan (PG). In addition to MltG, the previously identified physiological Prc substrates MepS and PBP3 are involved in PG biogenesis, suggesting a potential role of Prc in regulating PG biogenesis.
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Affiliation(s)
- Po-Chuen Hsu
- Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Chien-Sheng Chen
- Department of Food Safety/Hygiene and Risk Management, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Shuying Wang
- Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Center of Infectious Disease and Signaling Research, National Cheng Kung University, Tainan, Taiwan.,Department of Biotechnology and Bioindustry Sciences, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan, Taiwan
| | - Masayuki Hashimoto
- Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Center of Infectious Disease and Signaling Research, National Cheng Kung University, Tainan, Taiwan
| | - Wen-Chun Huang
- Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Ching-Hao Teng
- Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Center of Infectious Disease and Signaling Research, National Cheng Kung University, Tainan, Taiwan
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7
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Vestö K, Huseby DL, Snygg I, Wang H, Hughes D, Rhen M. Corrigendum: Muramyl Endopeptidase Spr Contributes to Intrinsic Vancomycin Resistance in Salmonella enterica Serovar Typhimurium. Front Microbiol 2019; 10:386. [PMID: 30891016 PMCID: PMC6411684 DOI: 10.3389/fmicb.2019.00386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 02/13/2019] [Indexed: 11/18/2022] Open
Affiliation(s)
- Kim Vestö
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Douglas L Huseby
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Iina Snygg
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Helen Wang
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.,Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Diarmaid Hughes
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Mikael Rhen
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.,Laboratory for Molecular Infection Medicine Sweden (MIMS), Department of Molecular Biology, Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
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8
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Vestö K, Huseby DL, Snygg I, Wang H, Hughes D, Rhen M. Muramyl Endopeptidase Spr Contributes to Intrinsic Vancomycin Resistance in Salmonella enterica Serovar Typhimurium. Front Microbiol 2018; 9:2941. [PMID: 30619108 PMCID: PMC6301998 DOI: 10.3389/fmicb.2018.02941] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Accepted: 11/15/2018] [Indexed: 12/13/2022] Open
Abstract
The impermeability barrier provided by the outer membrane of enteric bacteria, a feature lacking in Gram-positive bacteria, plays a major role in maintaining resistance to numerous antimicrobial compounds and antibiotics. Here we demonstrate that mutational inactivation of spr, coding for a muramyl endopeptidase, significantly sensitizes Salmonella enterica serovar Typhimurium to vancomycin without any accompanying apparent growth defect or outer membrane destabilization. A similar phenotype was not achieved by deleting the genes coding for muramyl endopeptidases MepA, PbpG, NlpC, YedA, or YhdO. The spr mutant showed increased autolytic behavior in response to not only vancomycin, but also to penicillin G, an antibiotic for which the mutant displayed a wild-type MIC. A screen for suppressor mutations of the spr mutant phenotype revealed that deletion of tsp (prc), encoding a periplasmic carboxypeptidase involved in processing Spr and PBP3, restored intrinsic resistance to vancomycin and reversed the autolytic phenotype of the spr mutant. Our data suggest that Spr contributes to intrinsic antibiotic resistance in S. Typhimurium without directly affecting the outer membrane permeability barrier. Furthermore, our data suggests that compounds targeting specific cell wall endopeptidases might have the potential to expand the activity spectrum of traditional Gram-positive antibiotics.
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Affiliation(s)
- Kim Vestö
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Douglas L. Huseby
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Iina Snygg
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Helen Wang
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Diarmaid Hughes
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Mikael Rhen
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
- Laboratory for Molecular Infection Medicine Sweden (MIMS), Department of Molecular Biology, Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
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9
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Singh SK, Parveen S, SaiSree L, Reddy M. Regulated proteolysis of a cross-link-specific peptidoglycan hydrolase contributes to bacterial morphogenesis. Proc Natl Acad Sci U S A 2015; 112:10956-61. [PMID: 26283368 DOI: 10.1073/pnas.1507760112] [Citation(s) in RCA: 86] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bacterial growth and morphogenesis are intimately coupled to expansion of peptidoglycan (PG), an extensively cross-linked macromolecule that forms a protective mesh-like sacculus around the cytoplasmic membrane. Growth of the PG sacculus is a dynamic event requiring the concerted action of hydrolases that cleave the cross-links for insertion of new material and synthases that catalyze cross-link formation; however, the factors that regulate PG expansion during bacterial growth are poorly understood. Here, we show that the PG hydrolase MepS (formerly Spr), which is specific to cleavage of cross-links during PG expansion in Escherichia coli, is modulated by proteolysis. Using combined genetic, molecular, and biochemical approaches, we demonstrate that MepS is rapidly degraded by a proteolytic system comprising an outer membrane lipoprotein of unknown function, NlpI, and a periplasmic protease, Prc (or Tsp). In summary, our results indicate that the NlpI-Prc system contributes to growth and enlargement of the PG sacculus by modulating the cellular levels of the cross-link-cleaving hydrolase MepS. Overall, this study signifies the importance of PG cross-link cleavage and its regulation in bacterial cell wall biogenesis.
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