Conformational behavior of the polysaccharide backbone of murein

Leps, Bernd; Labischinski, Harald; Bradaczek, H.

doi:10.1002/bip.360260813

Cited by 11 publications

(15 citation statements)

References 56 publications

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“…Peptidoglycan strands have a natural right-handed twist (15,30), nascent (17) and whole material (Fig. 2 C and D) is arranged helically, and cells of B. subtilis can grow helically under some conditions (18).…”

Section: Discussionmentioning

confidence: 99%

Cell wall peptidoglycan architecture in Bacillus subtilis

Hayhurst

Kailas

Hobbs

et al. 2008

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

217

227

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The bacterial cell wall is essential for viability and shape determination. Cell wall structural dynamics allowing growth and division, while maintaining integrity is a basic problem governing the life of bacteria. The polymer peptidoglycan is the main structural component for most bacteria and is made up of glycan strands that are cross-linked by peptide side chains. Despite study and speculation over many years, peptidoglycan architecture has remained largely elusive. Here, we show that the model rod-shaped bacterium Bacillus subtilis has glycan strands up to 5 m, longer than the cell itself and 50 times longer than previously proposed. Atomic force microscopy revealed the glycan strands to be part of a peptidoglycan architecture allowing cell growth and division. The inner surface of the cell wall has a regular macrostructure with Ϸ50 nm-wide peptidoglycan cables [average 53 ؎ 12 nm (n ‫؍‬ 91)] running basically across the short axis of the cell. Cross striations with an average periodicity of 25 ؎ 9 nm (n ‫؍‬ 96) along each cable are also present. The fundamental cabling architecture is also maintained during septal development as part of cell division. We propose a coiled-coil model for peptidoglycan architecture encompassing our data and recent evidence concerning the biosynthetic machinery for this essential polymer.

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Section: Discussionmentioning

confidence: 99%

Cell wall peptidoglycan architecture in Bacillus subtilis

Hayhurst

Kailas

Hobbs

et al. 2008

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

217

227

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“…Instead, the presence of the rather bulky lactyl group at MurNAc allows less rotation. About four disaccharide units (eight sugar residues) are required for one turn, and consequently, the peptides protrude from the glycans in a helical pattern (3,50,55) (Fig. 1B).…”

Section: Structural Modelsmentioning

confidence: 99%

The Architecture of the Murein (Peptidoglycan) in Gram-Negative Bacteria: Vertical Scaffold or Horizontal Layer(s)?

2004

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The murein (peptidoglycan) sacculus is the essential exoskeleton of all eubacteria (except Mycoplasma species and a few other species) that is needed to withstand the internal cytoplasmic turgor (osmotic) pressure (60,78). Murein consists of oligo(GlcNAc-MurNAc) glycan strands that are crosslinked by short peptides and thus form a net-like polymeric structure that surrounds the cytoplasmic membrane (78). The sacculus of Escherichia coli is one giant macromolecule with a molecular mass of more than 3 ϫ 10 9 Da, which is in the same range as the molecular mass of the chromosome of this bacterium (2.32 ϫ 10 9 Da). Moreover, the sacculus is embedded in the cell envelope by virtue of its location in the periplasm of gram-negative bacteria. It carries approximately 10 5 molecules of covalently bound lipoprotein (Lpp, Braun's lipoprotein) that links the outer membrane to the murein (6). It has been assumed that the murein glycans and peptides are arranged parallel to the membrane, forming a thin layer in gram-negative species and a thick multilayer structure in gram-positive species. This concept was challenged recently by Dmitriev et al. (20,21), who proposed the scaffold model, in which the murein glycan strands extend perpendicular to the cytoplasmic membrane. In this communication we first review relevant data on gram-negative murein structure and biosynthesis that were obtained over the past few decades in many laboratories, most of which were obtained from studies of E. coli. Then we discuss these findings with respect to different structural models of the murein sacculus. EXPERIMENTAL DATASize of the murein sacculus. The murein was isolated from gram-negative bacteria by boiling the cells in a sodium dodecyl sulfate (SDS) solution, followed by purification by enzymatic removal of glycogen and proteins (26,56,78). As visualized by electron microscopy, the purified murein sacculi are bagshaped structures with the dimensions and form of the bacteria from which they were isolated (Table 1). Like the rod-shaped cells, the sacculi of E. coli consist of a cylindrical part that is closed by two polar hemispherical regions. Compared to the length (about 2 to 4 m) and the diameter (about 0.5 to 1 m) of the sacculi, the murein is very thin, which results in the observed appearance of an empty and sometimes crumpled envelope laying flat on a grid used for electron microscopy (18,22,78).Thickness of murein. Three methods have been used to measure the thickness of the murein of E. coli: electron microscopy, neutron scattering, and atomic force microscopy. The results obtained by electron microscopy were different when different techniques were used (4). After successive fixation of cells with glutaraldehyde, osmium, and uranyl acetate, followed by dehydration with ethanol and embedding in araldite, De Petris observed a multilayer architecture for the cell envelope (19). One layer (the g 2 layer) disappeared completely upon treatment with the murein hydrolase lysozyme and was therefore identified as the murein layer. The g 2 ...

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“…This pentapeptide stem participates in an interglycan cross-linking reaction, thus creating the cell wall polymer. In contrast to the two other ␤-1,4-linked glycan biopolymers, cellulose (repeating glucose) (1)(2)(3)(4) and chitin (repeating NAG) (5-7) for which the 3D structure is solved, the structure of the bacterial cell wall has remained elusive because of its complexity and the lack of pure and discrete segments for structural study (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). Herein we describe the 3D structure, determined in aqueous solution by NMR, of a 2-kDa synthetic NAG-NAM(pentapeptide)-NAG-NAM(pentapeptide) tetrasaccharide cell wall segment.…”

mentioning

confidence: 99%

“…Because of the critical significance of the cell wall to bacterial survival, and the exploitation of the cell wall biosynthetic enzymes for the chemotherapeutic intervention of infections, many experimental and theoretical studies have addressed the cell wall structure. Despite diffraction studies carried out Ͼ30 years ago on cell wall extracted from bacteria, which strongly suggested that the peptidoglycan polymer possessed regular order (11), the 3D structure of the cell wall is not known. An excellent account of the historical development of the hypotheses for the cell wall structure is given by Dmitriev, Toukach, and Ehlers in their recent review (18).…”

mentioning

confidence: 99%

Three-dimensional structure of the bacterial cell wall peptidoglycan

Meroueh

Bencze

Hesek

et al. 2006

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

361

333

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The 3D structure of the bacterial peptidoglycan, the major constituent of the cell wall, is one of the most important, yet still unsolved, structural problems in biochemistry. The peptidoglycan comprises alternating N-acetylglucosamine (NAG) and N-acetylmuramic disaccharide (NAM) saccharides, the latter of which has a peptide stem. Adjacent peptide stems are cross-linked by the transpeptidase enzymes of cell wall biosynthesis to provide the cell wall polymer with the structural integrity required by the bacterium. The cell wall and its biosynthetic enzymes are targets of antibiotics. The 3D structure of the cell wall has been elusive because of its complexity and the lack of pure samples. Herein we report the 3D solution structure as determined by NMR of the 2-kDa NAG-NAM(pentapeptide)-NAG-NAM(pentapeptide) synthetic fragment of the cell wall. The glycan backbone of this peptidoglycan forms a right-handed helix with a periodicity of three for the NAG-NAM repeat (per turn of the helix). The first two amino acids of the pentapeptide adopt a limited number of conformations. Based on this structure a model for the bacterial cell wall is proposed. This pentapeptide stem participates in an interglycan cross-linking reaction, thus creating the cell wall polymer. In contrast to the two other ␤-1,4-linked glycan biopolymers, cellulose (repeating glucose) (1-4) and chitin (repeating NAG) (5-7) for which the 3D structure is solved, the structure of the bacterial cell wall has remained elusive because of its complexity and the lack of pure and discrete segments for structural study (8-18). Herein we describe the 3D structure, determined in aqueous solution by NMR, of a 2-kDa synthetic NAG-NAM(pentapeptide)-NAG-NAM(pentapeptide) tetrasaccharide cell wall segment. The defining aspect of this structure is an ordered, right-handed helical saccharide conformation corresponding to three NAG-NAM pairs per turn of the helix. The structure of this peptidoglycan segment is the basis for a proposal for the structure of the bacterial cell wall polymer.Results and Discussion 3D Structure of the Peptidoglycan. Because of the critical significance of the cell wall to bacterial survival, and the exploitation of the cell wall biosynthetic enzymes for the chemotherapeutic intervention of infections, many experimental and theoretical studies have addressed the cell wall structure. Despite diffraction studies carried out Ͼ30 years ago on cell wall extracted from bacteria, which strongly suggested that the peptidoglycan polymer possessed regular order (11), the 3D structure of the cell wall is not known. An excellent account of the historical development of the hypotheses for the cell wall structure is given by Dmitriev, Toukach, and Ehlers in their recent review (18). The major reason for the lack of progress is the absence of a pure fragment of the cell wall, having both the peptide and disaccharide components of the peptidoglycan, for structural investigation. To address this limitation we completed the 37-step synthesis of such a segment (1...

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Conformational behavior of the polysaccharide backbone of murein

Cited by 11 publications

References 56 publications

Cell wall peptidoglycan architecture in Bacillus subtilis

Cell wall peptidoglycan architecture in Bacillus subtilis

The Architecture of the Murein (Peptidoglycan) in Gram-Negative Bacteria: Vertical Scaffold or Horizontal Layer(s)?

Three-dimensional structure of the bacterial cell wall peptidoglycan

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