Peptidoglycan Hydrolases of Escherichia coli

Heijenoort, Jean van

doi:10.1128/mmbr.00022-11

Cited by 187 publications

(240 citation statements)

References 323 publications

(572 reference statements)

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“…It was proposed in the 'three-for-one' model that PG turnover is a result of a PG remodeling mechanism that replaces one existing strand with three new strands (12). E. coli has many glycosidases, but puzzlingly, none of them have been shown to be essential (2,45). Our simulations suggest a different explanation for how PG is released: glycosidases cleave loose uncrosslinked PG tails.…”

Section: Discussionmentioning

confidence: 58%

“…The second strategy would involve glycosidases that target PG tails but not crosslinked PG. E. coli does, in fact, have multiple glycosidases, but how they are regulated is not known (2,45). If they were free to cleave any glycosidic bond, presumably the cell would lyse.…”

Section: Resultsmentioning

confidence: 99%

“…Sacculus growth requires at least three types of enzymes: transglycosylases to synthesize new glycan strands, transpeptidases to crosslink them together, and endopeptidases to cleave existing peptide crosslinks to open space for new material (9,42,43). E. coli has other hydrolases that can modify PG, but none of them have been shown to be essential for rod shape maintenance (2,44,45). Thus, in our initial simulations, we simply introduced transglycosylases, transpeptidases, and endopeptidases onto the surface of the sacculus and modeled what happened as they diffused around performing their functions.…”

Section: Resultsmentioning

confidence: 99%

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Coarse-grained simulations of bacterial cell wall growth reveal that local coordination alone can be sufficient to maintain rod shape

Nguyen

Gumbart

Beeby

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Bacteria are surrounded by a peptidoglycan (PG) cell wall that must be remodeled to allow cell growth. While many structural details and properties of PG and the individual enzymes involved are known, how the process is coordinated to maintain cell integrity and rod shape is not understood. We have developed a coarse-grained method to simulate how individual transglycosylases, transpeptidases, and endopeptidases could introduce new material into an existing unilayer PG network. We find that a simple model with no enzyme coordination fails to maintain cell wall integrity and rod shape. We then iteratively analyze failure modes and explore different mechanistic hypotheses about how each problem might be overcome by the macromolecules involved. In contrast to a current theory, which posits that long MreB filaments are needed to coordinate PG insertion sites, we find that local coordination of enzyme activities in individual complexes can be sufficient to maintain cell integrity and rod shape. We also present possible molecular explanations for the existence of monofunctional transpeptidases and glycosidases (glycoside hydrolases), trimeric peptide crosslinks, cell twisting during growth, and synthesis of new strands in pairs.coarse-grained modeling | cell wall synthesis | morphogenesis T he cytoplasmic membrane of Gram-negative rod-shaped bacteria is surrounded by a peptidoglycan (PG) sacculus that protects the cell from internal turgor pressure, and its architecture determines the cell's shape (1, 2). The sacculus is composed of long glycan strands crosslinked by peptides into a mesh-like network. The glycan repeating unit is a disaccharide of an N-acetylglucosamine and an N-acetylmuramic acid attached to a stem pentapeptide L-Ala-D-iGlu-m-A 2 pm-D-Ala-D-Ala. Crosslinks are formed between peptides on adjacent strands-most at the fourth (D-Ala) residues of the donors and the third (m-A 2 pm) residues of the acceptors. While it is now understood that, in Gram-negative cells, the glycan strands run parallel to the cell surface, how the strands are arranged in this plane is still debated. While recent atomic force microscopy images of purified sacculi were interpreted to indicate that glycan strands had random orientations (3), electron cryotomography of sacculi (4) and other evidence from both Gramnegative (1, 5) and -positive (6, 7) sacculi have, instead, pointed to a universal "circumferential" model, in which the stiff glycan strands are circumferentially around the rod and the flexible peptide crosslinks parallel to the rod's long axis.Cell growth requires that the sacculus be elongated without losing its integrity or characteristic shape. This remodeling process requires the presence of not only transglycosylases and transpeptidases, also known as penicillin-binding proteins (PBPs), to polymerize and crosslink new glycan strands into the existing network (2, 8) but also, endopeptidases to cleave covalent bonds to open space for the new material (9). How these small enzymes work together to maintain the order and...

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Section: Discussionmentioning

confidence: 58%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Coarse-grained simulations of bacterial cell wall growth reveal that local coordination alone can be sufficient to maintain rod shape

Nguyen

Gumbart

Beeby

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…Thus, flagellar assembly would require the activity of an endo-acting lytic to create these pores along the PG sacculus at varying positions distinct from regions of continuing growth or division where other autolysins (e.g. LTs) function (11)(12)(13)15). This study introduces the first characterized ␤-N-acetylglucosaminidase found in Gram-negative bacteria.…”

Section: Discussionmentioning

confidence: 99%

The Essential Protein for Bacterial Flagella Formation FlgJ Functions as a β-N-Acetylglucosaminidase

Herlihey

Moynihan

Clarke

2014

Journal of Biological Chemistry

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Background: FlgJ is required for flagella formation in Salmonella enterica. Results: The lytic activity of FlgJ was determined to be that of a ␤-N-acetylglucosaminidase using a novel assay. Conclusion: FlgJ is a hydrolase and not a lytic transglycosylase. Significance: This information is essential for the search and rational design of inhibitors that may serve as leads to a new class of antibiotics.

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“…In many bacteria, including E. coli, the glycan backbone of PG is degraded by LTs that cleave the β-1,4 glycosidic bond via a mechanism that creates a 1,6-anhydroMurNAc end (7,24,25). Thus, denuded glycans generated by cell-wall amidases are expected to persist longer and accumulate to higher than normal levels in an LT mutant.…”

Section: Spor Domains Bind Septal Regions Of Purifiedmentioning

confidence: 99%

Bacterial SPOR domains are recruited to septal peptidoglycan by binding to glycan strands that lack stem peptides

Yahashiri

Jorgenson

Weiss

2015

Proc. Natl. Acad. Sci. U.S.A.

142

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Bacterial SPOR domains bind peptidoglycan (PG) and are thought to target proteins to the cell division site by binding to "denuded" glycan strands that lack stem peptides, but uncertainties remain, in part because septal-specific binding has yet to be studied in a purified system. Here we show that fusions of GFP to SPOR domains from the Escherichia coli cell-division proteins DamX, DedD, FtsN, and RlpA all localize to septal regions of purified PG sacculi obtained from E. coli and Bacillus subtilis. Treatment of sacculi with an amidase that removes stem peptides enhanced SPOR domain binding, whereas treatment with a lytic transglycosylase that removes denuded glycans reduced SPOR domain binding. These findings demonstrate unequivocally that SPOR domains localize by binding to septal PG, that the physiologically relevant binding site is indeed a denuded glycan, and that denuded glycans are enriched in septal PG rather than distributed uniformly around the sacculus. Accumulation of denuded glycans in the septal PG of both E. coli and B. subtilis, organisms separated by 1 billion years of evolution, suggests that sequential removal of stem peptides followed by degradation of the glycan backbone is an ancient feature of PG turnover during bacterial cell division. Linking SPOR domain localization to the abundance of a structure (denuded glycans) present only transiently during biogenesis of septal PG provides a mechanism for coordinating the function of SPOR domain proteins with the progress of cell division.A defining feature of bacteria is the peptidoglycan (PG) cell wall or "sacculus" that confers cell shape, protects the cell against lysis caused by turgor pressure, and is the ultimate target of many clinically relevant antibiotics, including β-lactams and vancomycin (1-4). The structure of PG is characterized by a network of glycan strands connected at regular intervals by oligopeptide cross-links (Fig. 1). The glycans are built from a repeating disaccharide of β-1,4-linked N-acetylglucosamine (GlcNAc) and N-acetylmuramic acid (MurNAc), from which branch the oligopeptides that mediate cross-linking. During cell division, a new PG wall is assembled between the incipient daughter cells (5, 6), and subsequent cell separation depends on the activity of a collection of PG hydrolases that cleave various bonds in the PG mesh (7).In the model Gram-negative bacterium Escherichia coli, daughter-cell separation is driven primarily by three cell-wall amidases (8-10). These enzymes cleave the amide bond that joins the lactyl group of the MurNAc to the α-amino group of the first amino acid (L-Ala) of the stem peptide, releasing as products free oligopeptides and "denuded" glycan strands (Fig. 1). Lytic transglycosylases (LTs) that cleave the MurNAc-GlcNAc glycosidic bond and endopeptidases that cleave stem peptides make minor but still significant contributions to daughter-cell separation (9, 11). In Bacillus subtilis, a model Gram-positive species, the enzymology of daughter-cell separation is not as well characterized. The...

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Peptidoglycan Hydrolases of Escherichia coli

Cited by 187 publications

References 323 publications

Coarse-grained simulations of bacterial cell wall growth reveal that local coordination alone can be sufficient to maintain rod shape

Coarse-grained simulations of bacterial cell wall growth reveal that local coordination alone can be sufficient to maintain rod shape

The Essential Protein for Bacterial Flagella Formation FlgJ Functions as a β-N-Acetylglucosaminidase

Bacterial SPOR domains are recruited to septal peptidoglycan by binding to glycan strands that lack stem peptides

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