Formation of the glycan chains in the synthesis of bacterial peptidoglycan

Heijenoort, Jean van

doi:10.1093/glycob/11.3.25r

Cited by 454 publications

(411 citation statements)

References 150 publications

(178 reference statements)

Supporting

Mentioning

396

Contrasting

Unclassified

Order By: Relevance

“…Glycosyl transfer by PGTs is thought to proceed by elongation at the reducing end of the growing polymer (24,25). It has also been suggested that PGTs are processive, meaning that they catalyze multiple rounds of coupling without releasing the elongating product; however, no definitive evidence for processivity has been presented.…”

Section: Resultsmentioning

confidence: 99%

Crystal structure of a peptidoglycan glycosyltransferase suggests a model for processive glycan chain synthesis

Yuan

Barrett²,

Zhang³

et al. 2007

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

138

122

View full text Add to dashboard Cite

Peptidoglycan is an essential polymer that forms a protective shell around bacterial cell membranes. Peptidoglycan biosynthesis is the target of many clinically used antibiotics, including the ␤-lactams, imipenems, cephalosporins, and glycopeptides. Resistance to these and other antibiotics has prompted interest in an atomic-level understanding of the enzymes that make peptidoglycan. Representative structures have been reported for most of the enzymes in the pathway. Until now, however, there have been no structures of any peptidoglycan glycosyltransferases (also known as transglycosylases), which catalyze formation of the carbohydrate chains of peptidoglycan from disaccharide subunits on the bacterial cell surface. We report here the 2.1-Å crystal structure of the peptidoglycan glycosyltransferase (PGT) domain of Aquifex aeolicus PBP1A. The structure has a different fold from all other glycosyltransferase structures reported to date, but it bears some resemblance to -lysozyme, an enzyme that degrades the carbohydrate chains of peptidoglycan. An analysis of the structure, combined with biochemical information showing that these enzymes are processive, suggests a model for glycan chain polymerization.antibiotic resistance ͉ penicillin-binding protein ͉ cell wall ͉ transglycosylase T he major component of the bacterial cell wall is a cross-linked glycopeptide polymer called peptidoglycan. This polymer surrounds the cytoplasmic membrane of bacteria and functions as an exoskeleton, maintaining cell shape and stabilizing the membrane against fluctuations in osmotic pressure. Peptidoglycan is synthesized in an intracellular phase in which UDP-Nacetylglucosamine is converted to a diphospholipid-linked disaccharide-pentapeptide known as Lipid II, and in an extracellular phase in which the disaccharide (NAG-NAM) subunits of translocated Lipid II are coupled by peptidoglycan glycosyltransferases (PGTs; also known as transglycosylases) to form linear carbohydrate chains ( Fig. 1), which are cross-linked through the attached peptide moieties by transpeptidases (1). A functioning peptidoglycan pathway is required for bacterial cell growth and division, and compounds that inhibit peptidoglycan biosynthesis have antibiotic activity (2). For example, the ␤-lactams, which have been used for decades to treat bacterial infections, irreversibly inhibit the transpeptidases. The emergence of resistance to ␤-lactams and other clinically used antibiotics has prompted intense interest in understanding peptidoglycan biosynthesis in detail. Major advances have been made in recent years with respect to the characterization of key biosynthetic enzymes (3-5). Several structures have been reported for enzymes that catalyze transpeptidation (6, 7), but no PGT structures have been described.PGTs are defined by the presence of five conserved sequence motifs ( Fig. 2A) and exist in two forms: (i) as N-terminal glycosyltransferase domains in bifunctional proteins that also contain a C-terminal transpeptidase domain [called class A penicillin-bindi...

show abstract

Section: Resultsmentioning

confidence: 99%

Crystal structure of a peptidoglycan glycosyltransferase suggests a model for processive glycan chain synthesis

Yuan

Barrett²,

Zhang³

et al. 2007

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

138

122

View full text Add to dashboard Cite

show abstract

“…Polymerization of the peptidoglycan subunit at the cell surface is performed by glycosyltransferases that catalyze elongation of the glycan strands by formation of ␤-1,4 bonds and D,D-transpeptidases that cross-link glycan strands (4). The latter reaction is catalyzed by essential high molecular weight penicillin-binding proteins (PBPs) that cleave the C-terminal residue (D-Ala 5 ) of a donor stem peptide and link the carboxyl group of the penultimate residue (D-Ala 4 ) to the side chain amino group of an acceptor stem peptide (5) (see Fig.…”

Section: ) (3)mentioning

confidence: 99%

Synthesis of Mosaic Peptidoglycan Cross-bridges by Hybrid Peptidoglycan Assembly Pathways in Gram-positive Bacteria

Arbeloa

Hugonnet

Sentilhes

et al. 2004

Journal of Biological Chemistry

View full text Add to dashboard Cite

The peptidoglycan cross-bridges of Staphylococcus aureus, Enterococcus faecalis, and Enterococcus faecium consist of the sequences Gly 5 , L-Ala 2 , and D-Asx, respectively. Expression of the fmhB, femA, and femB genes of S. aureus in E. faecalis led to the production of peptidoglycan precursors substituted by mosaic side chains that were efficiently used by the penicillin-binding proteins for cross-bridge formation. The Fem transferases were specific for incorporation of glycyl residues at defined positions of the side chains in the absence of any additional S. aureus factors such as tRNAs used for amino acid activation. The PBPs of E. faecalis displayed a broad substrate specificity because mosaic side chains containing from 1 to 5 residues and Gly instead of L-Ala at the N-terminal position were used for peptidoglycan cross-linking. Low affinity PBP2a of S. aureus conferred ␤-lactam resistance in E. faecalis and E. faecium, thereby indicating that there was no barrier to heterospecific expression of resistance caused by variations in the structure of peptidoglycan precursors. Thus, conservation of the structure of the peptidoglycan cross-bridges in members of the same species reflects the high specificity of the enzymes for side chain synthesis, although this is not essential for the activity of the PBPs.

show abstract

“…It is a single, covalently closed molecule, and thus bonds must be broken to generate sites for the insertion of new PG subunits (6). At such sites, penicillin-binding proteins (PBPs) processively elongate glycan strands by adding new subunits to their growing ends (7)(8)(9)(10). According to the three-for-one model, a popular model for PG insertion, three new glycan strands are believed to be linked to the existing PG by cross-linking to both sides of a docking strand on the preexisting PG.…”

mentioning

confidence: 99%

Processivity of peptidoglycan synthesis provides a built-in mechanism for the robustness of straight-rod cell morphology

Sliusarenko

Cabeen

Wolgemuth

et al. 2010

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

View full text Add to dashboard Cite

The propagation of cell shape across generations is remarkably robust in most bacteria. Even when deformations are acquired, growing cells progressively recover their original shape once the deforming factors are eliminated. For instance, straight-rod-shaped bacteria grow curved when confined to circular microchambers, but straighten in a growth-dependent fashion when released. Bacterial cell shape is maintained by the peptidoglycan (PG) cell wall, a giant macromolecule of glycan strands that are synthesized by processive enzymes and cross-linked by peptide chains. Changes in cell geometry require modifying the PG and therefore depend directly on the molecular-scale properties of PG structure and synthesis. Using a mathematical model we quantify the straightening of curved Caulobacter crescentus cells after disruption of the cell-curving crescentin structure. We observe that cells straighten at a rate that is about half (57%) the cell growth rate. Next we show that in the absence of other effects there exists a mathematical relationship between the rate of cell straightening and the processivity of PG synthesis-the number of subunits incorporated before termination of synthesis. From the measured rate of cell straightening this relationship predicts processivity values that are in good agreement with our estimates from published data. Finally, we consider the possible role of three other mechanisms in cell straightening. We conclude that regardless of the involvement of other factors, intrinsic properties of PG processivity provide a robust mechanism for cell straightening that is hardwired to the cell wall synthesis machinery.cell shape | cell wall | cell curvature | modeling B acteria exhibit a wide variety of shapes, which are precisely maintained over countless generations in most species, though the mechanisms of the process are not well understood. Many bacteria display rod shape, which can confer selective advantages (1). In nature bacteria frequently grow in dense environments such as soil and colonies, and are therefore likely to experience physical constraints. For example, chemotactic rodshaped bacteria are capable of penetrating channels narrower than their diameter to reach nutrient sources. Within the channels, growing and dividing cells undergo significant mechanical stress and acquire various deformed cell shapes (2). Similarly, recent experiments using microchambers showed that external physical forces can cause straight-rod-shaped cells to grow curved (3,4). Once the force is released, cells gradually return to their native straight-rod shape as growth continues (2-4). The properties of cell shape recovery have not received much attention, yet they have important implications for the robust maintenance of cell shape throughout bacterial populations.Here we focus on the straightening of curved rod-shaped cells. Using a mathematical model we show first that straightening of exponentially growing cells is a rather surprising phenomenon that would not occur without a specific mechanism. We then dis...

show abstract

Formation of the glycan chains in the synthesis of bacterial peptidoglycan

Cited by 454 publications

References 150 publications

Crystal structure of a peptidoglycan glycosyltransferase suggests a model for processive glycan chain synthesis

Crystal structure of a peptidoglycan glycosyltransferase suggests a model for processive glycan chain synthesis

Synthesis of Mosaic Peptidoglycan Cross-bridges by Hybrid Peptidoglycan Assembly Pathways in Gram-positive Bacteria

Processivity of peptidoglycan synthesis provides a built-in mechanism for the robustness of straight-rod cell morphology

Contact Info

Product

Resources

About