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1. (CSDB ID: 8499) | report error |
| Pyr-(2-6:2-4)-+ | -3)-b-D-ManpNAc-(1-4)-b-D-GlcpNAc-(1- | Show graphically |
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Paenibacillus alvei CCM 2051T
(Ancestor NCBI TaxID 44250,
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uvic.ca>Self-assembling (glyco)protein surface layers (S-layers) are ubiquitous prokaryotic cell-surface structures involved in structural maintenance, nutrient diffusion, host adhesion, virulence, and other processes, which makes them appealing targets for therapeutics and biotechnological applications as biosensors or drug delivery systems. However, unlocking this potential requires expanding our understanding of S-layer properties, especially the details of surface-attachment. S-layers of Gram-positive bacteria often are attached through the interaction of S-layer homology (SLH) domain trimers with peptidoglycan-linked secondary cell wall polymers (SCWPs). Cocrystal structures of the SLH domain trimer from the Paenibacillus alvei S-layer protein SpaA (SpaASLH) with synthetic, terminal SCWP disaccharide and trisaccharide analogs, together with isothermal titration calorimetry binding analyses, reveal that while SpaASLH accommodates longer biologically relevant SCWP ligands within both its primary (G2) and secondary (G1) binding sites, the terminal pyruvylated ManNAc moiety serves as the nearly exclusive SCWP anchoring point. Binding is accompanied by displacement of a flexible loop adjacent to the receptor site that enhances the complementarity between protein and ligand, including electrostatic complementarity with the terminal pyruvate moiety. Remarkably, binding of the pyruvylated monosaccharide SCWP fragment alone is sufficient to cause rearrangement of the receptor-binding sites in a manner necessary to accommodate longer SCWP fragments. The observation of multiple conformations in longer oligosaccharides bound to the protein, together with the demonstrated functionality of two of the three SCWP receptor-binding sites, reveals how the SpaASLH-SCWP interaction has evolved to accommodate longer SCWP ligands and alleviate the strain inherent to bacterial S-layer adhesion during growth and division.
S-layer, X-ray crystallography, secondary cell wall polymer, cell wall anchoring, isothermal titration calorimetry, SLH domain
Structure type: polymer chemical repeating unit ; n=11|
2. (CSDB ID: 8557) | report error |
| a-D-Galp-(1-3)-+ a-D-Galp-(1-3)-+ a-D-Galp-(1-3)-+ a-D-Galp-(1-3)-+ | | | | S-Pyr-(2-6:2-4)-b-D-ManpNAc-(1-4)-b-D-GlcpNAc3Ac-(1-6)-a-D-GlcpN-(1-4)-{{{-b-D-ManpNAc-(1-4)-b-D-GlcpNAc-(1-6)-a-D-GlcpNAc-(1-4)-}}}/n=4-10/-b-D-ManpNAc-(1-4)-b-D-GlcpNAc-(1-6)-a-D-GlcpNAc | | b-D-Galp-(1-4)-+ b-D-Galp-(1-4)-+ | Show graphically |
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Bacillus anthracis
(NCBI TaxID 1392,
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]bsd.uchicago.edu>Bacillus anthracis elaborates a secondary cell wall polysaccharide (SCWP) made of 6 to 12 trisaccharide units. Pyruvyl and acetyl substitutions of the distal unit are prerequisites for the noncovalent retention of 22 secreted Bacillus S-layer (Bsl)-associated proteins bearing an S-layer homology (SLH) domain. Surface display of Bsl proteins contributes to cell separation as well as virulence. Earlier work suggested that TagO initiates the synthesis of SCWP while GneY and GneZ, two UDP-GlcNAc 2-epimerases, synthesize ManNAc that is later incorporated in the repeat unit (→4)-ManNAc-(β1→4)-GlcNAc-(β1→6)-GlcNAc-(α1→). In organisms that synthesize wall teichoic acid, TagA catalysts have been shown to form the glycosidic bond ManNAc-(β1→4)-GlcNAc. Here, we show that genes bas2675 and bas5272, predicted to encode glycosyltransferases of the WecB/TagA/CpsF family (PFAM03808; CAZy GT26), are required for B. anthracis SCWP synthesis and S-layer assembly. Similar to tagO or gneY gneZ mutants, B. anthracis strains depleted of tagA1 (bas5272) cannot maintain cell shape, support vegetative growth, or synthesize SCWP. Expression of tagA2 (bas2675), or Staphylococcus aureus tagA on a plasmid, rescues the nonviable tagA1 mutant. We propose that TagA1 and TagA2 fulfill overlapping and key glycosyltransferase functions for the synthesis of repeat units of the SCWP of B. anthracis. IMPORTANCE Glycosyltransferases (GTs) catalyze the transfer of sugar moieties from activated donor molecules to acceptor molecules to form glycosidic bonds using a retaining or inverting mechanism. Based on the structural relatedness of their catalytic and carbohydrate-binding modules, GTs have been grouped into 115 families in the Carbohydrate-Active EnZyme (CAZy) database. For complex products, the functional assignment of GTs remains highly challenging without the knowledge of the chemical structure of the assembled polymer. Here, we propose that two uncharacterized GTs of B. anthracis belonging to the WecB/TagA/CpsF family incorporate ManNAc in repeat units of the secondary cell wall polymer of bacilli species.
glycosyltransferase, Bacillus anthracis, secondary cell wall polysaccharide, envelope biogenesis, S-layer homology domain, TagA, UDP-N-acetyl-mannosamine, undecaprenol-phosphate
Structure type: structural motif or average structure| New query | Export IDs | Home | Help |
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