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Santin YG, Cascales E. Measure of Peptidoglycan Degradation Activity. Methods Mol Biol 2024; 2715:197-205. [PMID: 37930529 DOI: 10.1007/978-1-0716-3445-5_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2023]
Abstract
Most bacterial secretion systems are large machines that cross the cell envelope to deliver effectors outside the cell or directly into target cells. The peptidoglycan layer can therefore represent a physical barrier for the assembly of these large machines. Secretion systems and their counterparts such as type IV pili, flagella, and conjugation machines have therefore evolved or hijacked enzymes with peptidoglycan degradation activity. These enzymes are usually glycoside hydrolases that cleave the glycan chains of the peptidoglycan. Their activities are spatially controlled to avoid cell lysis and to create local rearrangement of the cell wall. In addition, peptidoglycan hydrolases may not be only required for the proper assembly of the secretion systems but may directly participate to the release of the effectors. Finally, several antibacterial effectors possess peptidoglycan degradation activity that damage the cell wall once delivered in the target cell. Here, we describe protocols to test the peptidoglycan degradation activity of these proteins in vitro and in solution.
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Affiliation(s)
- Yoann G Santin
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, UMR7255, Institut de Microbiologie de la Méditerranée, Aix-Marseille Univ, CNRS, Marseille, France
- de Duve Institute, UCLouvain, Brussels, Belgium
| | - Eric Cascales
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, UMR7255, Institut de Microbiologie de la Méditerranée, Aix-Marseille Univ, CNRS, Marseille, France.
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2
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Modulation of the enzymatic activity of the flagellar lytic transglycosylase SltF by rod components, and the scaffolding protein FlgJ in Rhodobacter sphaeroides. J Bacteriol 2021; 203:e0037221. [PMID: 34309398 DOI: 10.1128/jb.00372-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Macromolecular cell-envelope-spanning structures such as the bacterial flagellum must traverse the cell wall. Lytic transglycosylases enzymes are capable of enlarging gaps in the peptidoglycan meshwork to allow the efficient assembly of supramolecular complexes. In the periplasmic space, the assembly of the flagellar rod requires the scaffold protein FlgJ, which includes a muramidase domain in the canonical models Salmonella enterica and Escherichia coli. In contrast, in Rhodobacter sphaeroides, FlgJ and the dedicated flagellar lytic transglycosylase SltF are separate entities that interact in the periplasm. In this study we show that sltF is expressed along with the genes encoding the early components of the flagellar hierarchy that include the hook-basal body proteins, making SltF available during the rod assembly. Protein-protein interaction experiments demonstrated that SltF interacts with the rod proteins FliE, FlgB, FlgC, FlgF and FlgG through its C-terminal region. A deletion analysis that divides the C-terminus in two halves revealed that the interacting regions for most of the rod proteins are not redundant. Our results also show that the presence of the rod proteins FliE, FlgB, FlgC, and FlgF displace the previously reported SltF-FlgJ interaction. In addition, we observed modulation of the transglycosylase activity of SltF mediated by FlgB and FlgJ that could be relevant to coordinate rod assembly with cell wall remodeling. In summary, different mechanisms regulate the flagellar lytic transglycosylase, SltF ensuring a timely transcription, a proper localization and a controlled enzymatic activity. Importance Several mechanisms participate in the assembly of cell-envelope-spanning macromolecular structures. The sequential expression of substrates to be exported, selective export, and a specific order of incorporation are some of the mechanisms that stand out to drive an efficient assembly process. In this work we analyze how the structural rod proteins, the scaffold protein FlgJ and the flagellar lytic enzyme SltF, interact in an orderly fashion to assemble the flagellar rod into the periplasmic space. A complex arrangement of transient interactions directs a dedicated flagellar muramidase towards the flagellar rod. All these interactions bring this protein to the proximity of the peptidoglycan wall while also modulating its enzymatic activity. This study suggests how a dynamic network of interactions participates in controlling SltF, a prominent component for flagellar formation.
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3
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Nguyen BN, Chávez-Arroyo A, Cheng MI, Krasilnikov M, Louie A, Portnoy DA. TLR2 and endosomal TLR-mediated secretion of IL-10 and immune suppression in response to phagosome-confined Listeria monocytogenes. PLoS Pathog 2020; 16:e1008622. [PMID: 32634175 PMCID: PMC7340287 DOI: 10.1371/journal.ppat.1008622] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 05/12/2020] [Indexed: 01/24/2023] Open
Abstract
Listeria monocytogenes is a facultative intracellular bacterial pathogen that escapes from phagosomes and induces a robust adaptive immune response in mice, while mutants unable to escape phagosomes fail to induce a robust adaptive immune response and suppress the immunity to wildtype bacteria when co-administered. The capacity to suppress immunity can be reversed by blocking IL-10. In this study, we sought to understand the host receptors that lead to secretion of IL-10 in response to phagosome-confined L. monocytogenes (Δhly), with the ultimate goal of generating strains that fail to induce IL-10. We conducted a transposon screen to identify Δhly L. monocytogenes mutants that induced significantly more or less IL-10 secretion in bone marrow-derived macrophages (BMMs). A transposon insertion in lgt, which encodes phosphatidylglycerol-prolipoprotein diacylglyceryl transferase and is essential for the formation of lipoproteins, induced significantly reduced IL-10 secretion. Mutants with transposon insertions in pgdA and oatA, which encode peptidoglycan N-acetylglucosamine deacetylase and O-acetyltransferase, are sensitive to lysozyme and induced enhanced IL-10 secretion. A ΔhlyΔpgdAΔoatA strain was killed in BMMs and induced enhanced IL-10 secretion that was dependent on Unc93b1, a trafficking molecule required for signaling of nucleic acid-sensing TLRs. These data revealed that nucleic acids released by bacteriolysis triggered endosomal TLR-mediated IL-10 secretion. Secretion of IL-10 in response to infection with the parental strain was mostly TLR2-dependent, while IL-10 secretion in response to lysozyme-sensitive strains was dependent on TLR2 and Unc93b1. In mice, the IL-10 response to vacuole-confined L. monocytogenes was also dependent on TLR2 and Unc93b1. Co-administration of Δhly and ΔactA resulted in suppressed immunity in WT mice, but not in mice with mutations in Unc93b1. These data revealed that secretion of IL-10 in response to L. monocytogenes infection in vitro is mostly TLR2-dependent and immune suppression by phagosome-confined bacteria in vivo is mostly dependent on endosomal TLRs.
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Affiliation(s)
- Brittney N. Nguyen
- Graduate Group in Microbiology, University of California, Berkeley, Berkeley, California, United States of America
| | - Alfredo Chávez-Arroyo
- Graduate Group in Microbiology, University of California, Berkeley, Berkeley, California, United States of America
| | - Mandy I. Cheng
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, United States of America
| | - Maria Krasilnikov
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, United States of America
| | - Alexander Louie
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, United States of America
| | - Daniel A. Portnoy
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, United States of America
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, United States of America
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4
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Camarena L, Dreyfus G. Living in a Foster Home: The Single Subpolar Flagellum Fla1 of Rhodobacter sphaeroides. Biomolecules 2020; 10:E774. [PMID: 32429424 PMCID: PMC7277832 DOI: 10.3390/biom10050774] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2020] [Revised: 05/12/2020] [Accepted: 05/13/2020] [Indexed: 12/14/2022] Open
Abstract
Rhodobacter sphaeroides is an α-proteobacterium that has the particularity of having two functional flagellar systems used for swimming. Under the growth conditions commonly used in the laboratory, a single subpolar flagellum that traverses the cell membrane, is assembled on the surface. This flagellum has been named Fla1. Phylogenetic analyses have suggested that this flagellar genetic system was acquired from an ancient γ-proteobacterium. It has been shown that this flagellum has components homologous to those present in other γ-proteobacteria such as the H-ring characteristic of the Vibrio species. Other features of this flagellum such as a straight hook, and a prominent HAP region have been studied and the molecular basis underlying these features has been revealed. It has also been shown that FliL, and the protein MotF, mainly found in several species of the family Rhodobacteraceae, contribute to remodel the amphipathic region of MotB, known as the plug, in order to allow flagellar rotation. In the absence of the plug region of MotB, FliL and MotF are dispensable. In this review we have covered the most relevant aspects of the Fla1 flagellum of this remarkable photosynthetic bacterium.
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Affiliation(s)
- Laura Camarena
- Depto. Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, CDMX 04510, Mexico
| | - Georges Dreyfus
- Depto. Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad Universitaria, CDMX 04510, Mexico
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5
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Juan C, Torrens G, Barceló IM, Oliver A. Interplay between Peptidoglycan Biology and Virulence in Gram-Negative Pathogens. Microbiol Mol Biol Rev 2018; 82:e00033-18. [PMID: 30209071 PMCID: PMC6298613 DOI: 10.1128/mmbr.00033-18] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The clinical and epidemiological threat of the growing antimicrobial resistance in Gram-negative pathogens, particularly for β-lactams, the most frequently used and relevant antibiotics, urges research to find new therapeutic weapons to combat the infections caused by these microorganisms. An essential previous step in the development of these therapeutic solutions is to identify their potential targets in the biology of the pathogen. This is precisely what we sought to do in this review specifically regarding the barely exploited field analyzing the interplay among the biology of the peptidoglycan and related processes, such as β-lactamase regulation and virulence. Hence, here we gather, analyze, and integrate the knowledge derived from published works that provide information on the topic, starting with those dealing with the historically neglected essential role of the Gram-negative peptidoglycan in virulence, including structural, biogenesis, remodeling, and recycling aspects, in addition to proinflammatory and other interactions with the host. We also review the complex link between intrinsic β-lactamase production and peptidoglycan metabolism, as well as the biological costs potentially associated with the expression of horizontally acquired β-lactamases. Finally, we analyze the existing evidence from multiple perspectives to provide useful clues for identifying targets enabling the future development of therapeutic options attacking the peptidoglycan-virulence interconnection as a key weak point of the Gram-negative pathogens to be used, if not to kill the bacteria, to mitigate their capacity to produce severe infections.
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Affiliation(s)
- Carlos Juan
- Servicio de Microbiología and Unidad de Investigación, Hospital Son Espases, Instituto de Investigación Sanitaria de Baleares (IdISBa), Palma, Spain
| | - Gabriel Torrens
- Servicio de Microbiología and Unidad de Investigación, Hospital Son Espases, Instituto de Investigación Sanitaria de Baleares (IdISBa), Palma, Spain
| | - Isabel Maria Barceló
- Servicio de Microbiología and Unidad de Investigación, Hospital Son Espases, Instituto de Investigación Sanitaria de Baleares (IdISBa), Palma, Spain
| | - Antonio Oliver
- Servicio de Microbiología and Unidad de Investigación, Hospital Son Espases, Instituto de Investigación Sanitaria de Baleares (IdISBa), Palma, Spain
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6
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Crépin S, Ottosen EN, Peters K, Smith SN, Himpsl SD, Vollmer W, Mobley HLT. The lytic transglycosylase MltB connects membrane homeostasis and in vivo fitness of Acinetobacter baumannii. Mol Microbiol 2018; 109:745-762. [PMID: 29884996 PMCID: PMC6185781 DOI: 10.1111/mmi.14000] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 05/30/2018] [Accepted: 07/15/2018] [Indexed: 01/06/2023]
Abstract
Acinetobacter baumannii has emerged as a leading nosocomial pathogen, infecting a wide range of anatomic sites including the respiratory tract and the bloodstream. In addition to being multi‐drug resistant, little is known about the molecular basis of A. baumannii pathogenesis. To better understand A. baumannii virulence, a combination of a transposon‐sequencing (TraDIS) screen and the neutropenic mouse model of bacteremia was used to identify the full set of fitness genes required during bloodstream infection. The lytic transglycosylase MltB was identified as a critical fitness factor. MltB cleaves the MurNAc‐GlcNAc bond of peptidoglycan, which leads to cell wall remodeling. Here we show that MltB is part of a complex network connecting resistance to stresses, membrane homeostasis, biogenesis of pili and in vivo fitness. Indeed, inactivation of mltB not only impaired resistance to serum complement, cationic antimicrobial peptides and oxygen species, but also altered the cell envelope integrity, activated the envelope stress response, drastically reduced the number of pili at the cell surface and finally, significantly decreased colonization of both the bloodstream and the respiratory tract.
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Affiliation(s)
- Sébastien Crépin
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Elizabeth N Ottosen
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Katharina Peters
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, UK
| | - Sara N Smith
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Stephanie D Himpsl
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Waldemar Vollmer
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, UK
| | - Harry L T Mobley
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, USA
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7
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Biochemical and Phylogenetic Study of SltF, a Flagellar Lytic Transglycosylase from Rhodobacter sphaeroides. J Bacteriol 2018; 200:JB.00397-18. [PMID: 30061356 DOI: 10.1128/jb.00397-18] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Accepted: 07/27/2018] [Indexed: 11/20/2022] Open
Abstract
In this work, we have characterized the soluble lytic transglycosylase (SltF) from Rhodobacter sphaeroides that interacts with the scaffolding protein FlgJ in the periplasm to open space at the cell wall peptidoglycan heteropolymer for the emerging rod. The characterization of the genetic context of flgJ and sltF in alphaproteobacteria shows that these two separate genes coexist frequently in a flagellar gene cluster. Two domains of unknown function in SltF were studied, and the results show that the deletion of a 17-amino-acid segment near the N terminus does not show a recognizable phenotype, whereas the deletion of 47 and 95 amino acids of the C terminus of SltF disrupts the interaction with FlgJ without affecting the transglycosylase catalytic activity of SltF. These mutant proteins are unable to support swimming, indicating that the physical interaction between SltF and FlgJ is central for flagellar formation. In a maximum likelihood tree of representative lytic transglycosylases, all of the flagellar SltF proteins cluster in subfamily 1F. From this analysis, it was also revealed that the lytic transglycosylases related to the type III secretion systems present in pathogens cluster with the closely related flagellar transglycosylases.IMPORTANCE Flagellar biogenesis is a highly orchestrated event where the flagellar structure spans the bacterial cell envelope. The rod diameter of approximately 4 nm is larger than the estimated pore size of the peptidoglycan layer; hence, its insertion requires the localized and controlled lysis of the cell wall. We found that a 47-residue domain of the C terminus of the lytic transglycosylase (LT) SltF of R. sphaeroides is involved in the recognition of the rod chaperone FlgJ. We also found that in many alphaproteobacteria, the flagellar cluster includes a homolog of SltF and FlgJ, indicating that association of an LT with the flagellar machinery is ancestral. A maximum likelihood tree shows that family 1 of LTs segregates into seven subfamilies.
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8
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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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9
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Lee M, Hesek D, Dik DA, Fishovitz J, Lastochkin E, Boggess B, Fisher JF, Mobashery S. From Genome to Proteome to Elucidation of Reactions for All Eleven Known Lytic Transglycosylases from Pseudomonas aeruginosa. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201611279] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Mijoon Lee
- Department of Chemistry and Biochemistry; University of Notre Dame; Notre Dame IN 46556 USA
| | - Dusan Hesek
- Department of Chemistry and Biochemistry; University of Notre Dame; Notre Dame IN 46556 USA
| | - David A. Dik
- Department of Chemistry and Biochemistry; University of Notre Dame; Notre Dame IN 46556 USA
| | - Jennifer Fishovitz
- Department of Chemistry and Biochemistry; University of Notre Dame; Notre Dame IN 46556 USA
| | - Elena Lastochkin
- Department of Chemistry and Biochemistry; University of Notre Dame; Notre Dame IN 46556 USA
| | - Bill Boggess
- Department of Chemistry and Biochemistry; University of Notre Dame; Notre Dame IN 46556 USA
| | - Jed F. Fisher
- Department of Chemistry and Biochemistry; University of Notre Dame; Notre Dame IN 46556 USA
| | - Shahriar Mobashery
- Department of Chemistry and Biochemistry; University of Notre Dame; Notre Dame IN 46556 USA
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10
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Lee M, Hesek D, Dik DA, Fishovitz J, Lastochkin E, Boggess B, Fisher JF, Mobashery S. From Genome to Proteome to Elucidation of Reactions for All Eleven Known Lytic Transglycosylases from Pseudomonas aeruginosa. Angew Chem Int Ed Engl 2017; 56:2735-2739. [PMID: 28128504 DOI: 10.1002/anie.201611279] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Revised: 12/09/2016] [Indexed: 11/07/2022]
Abstract
An enzyme superfamily, the lytic transglycosylases (LTs), occupies the space between the two membranes of Gram-negative bacteria. LTs catalyze the non-hydrolytic cleavage of the bacterial peptidoglycan cell-wall polymer. This reaction is central to the growth of the cell wall, for excavating the cell wall for protein insertion, and for monitoring the cell wall so as to initiate resistance responses to cell-wall-acting antibiotics. The nefarious Gram-negative pathogen Pseudomonas aeruginosa encodes eleven LTs. With few exceptions, their substrates and functions are unknown. Each P. aeruginosa LT was expressed as a soluble protein and evaluated with a panel of substrates (both simple and complex mimetics of their natural substrates). Thirty-one distinct products distinguish these LTs with respect to substrate recognition, catalytic activity, and relative exolytic or endolytic ability. These properties are foundational to an understanding of the LTs as catalysts and as antibiotic targets.
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Affiliation(s)
- Mijoon Lee
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Dusan Hesek
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - David A Dik
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Jennifer Fishovitz
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Elena Lastochkin
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Bill Boggess
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Jed F Fisher
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Shahriar Mobashery
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
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11
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Carbohydrate recognition and lysis by bacterial peptidoglycan hydrolases. Curr Opin Struct Biol 2017; 44:87-100. [PMID: 28109980 DOI: 10.1016/j.sbi.2017.01.001] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 12/23/2016] [Accepted: 01/02/2017] [Indexed: 01/26/2023]
Abstract
The major component of bacterial cell wall is peptidoglycan (PG), a complex polymer formed by long glycan chains cross-linked by peptide stems. PG is in constant equilibrium requiring well-orchestrated coordination between synthesis and degradation. The resulting cell-wall fragments can be recycled, act as messengers for bacterial communication, as effector molecules in immune response or as signaling molecules triggering antibiotics resistance. Tailoring and recycling of PG requires the cleavage of different covalent bonds of the PG sacculi by a diverse set of specific enzymes whose activities are strictly regulated. Here, we review the molecular mechanisms that govern PG remodeling focusing on the structural information available for the bacterial lytic enzymes and the mechanisms by which they recognize their substrates.
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12
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Abstract
Most gene clusters encoding multiprotein complexes of the bacterial cell envelope, such as conjugation and secretion systems, Type IV pili, and flagella, bear a gene encoding an enzyme with peptidoglycan hydrolase activity. These enzymes are usually glycoside hydrolases that cleave the glycan chains of the peptidoglycan. Their activities are spatially controlled to avoid cell lysis and to create localized rearrangement of the cell wall. This is assured by interaction with the structural subunits of the apparatus. Here we describe protocols to test the peptidoglycan hydrolase activity of these proteins in vitro and in solution.
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13
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Santin YG, Cascales E. Domestication of a housekeeping transglycosylase for assembly of a Type VI secretion system. EMBO Rep 2016; 18:138-149. [PMID: 27920034 DOI: 10.15252/embr.201643206] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 10/27/2016] [Accepted: 10/28/2016] [Indexed: 01/06/2023] Open
Abstract
The type VI secretion system (T6SS) is an anti-bacterial weapon comprising a contractile tail anchored to the cell envelope by a membrane complex. The TssJ, TssL, and TssM proteins assemble a 1.7-MDa channel complex that spans the cell envelope, including the peptidoglycan layer. The electron microscopy structure of the TssJLM complex revealed that it has a diameter of ~18 nm in the periplasm, which is larger than the size of peptidoglycan pores (~2 nm), hence questioning how the T6SS membrane complex crosses the peptidoglycan layer. Here, we report that the MltE housekeeping lytic transglycosylase (LTG) is required for T6SS assembly in enteroaggregative Escherichia coli Protein-protein interaction studies further demonstrated that MltE is recruited to the periplasmic domain of TssM. In addition, we show that TssM significantly stimulates MltE activity in vitro and that MltE is required for the late stages of T6SS membrane complex assembly. Collectively, our data provide the first example of domestication and activation of a LTG encoded within the core genome for the assembly of a secretion system.
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Affiliation(s)
- Yoann G Santin
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), UMR 7255, Institut de Microbiologie de la Méditerranée, Aix-Marseille Univ - CNRS, Marseille Cedex 20, France
| | - Eric Cascales
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), UMR 7255, Institut de Microbiologie de la Méditerranée, Aix-Marseille Univ - CNRS, Marseille Cedex 20, France
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14
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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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