6fi2

VexL: A periplasmic depolymerase provides new insight into ABC transporter-dependent secretion of bacterial capsular polysaccharides

spinqualitylabelsall models 6fi2, resolution 1.22Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 6fi2 is a 1 chain structure with sequence from Achromobacter denitrificans. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.22Å Ligands: DJB, DJE, MLI Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function A0A160EBC2_ACHDE Publication Abstract from PubMed Capsules are surface layers of hydrated capsular polysaccharides (CPSs) produced by many bacteria. The human pathogen Salmonella enterica serovar Typhi produces "Vi antigen" CPS, which contributes to virulence. In a conserved strategy used by bacteria with diverse CPS structures, translocation of Vi antigen to the cell surface is driven by an ATP-binding cassette (ABC) transporter. These transporters are engaged in heterooligomeric complexes proposed to form an enclosed translocation conduit to the cell surface, allowing the transporter to power the entire process. We identified Vi antigen biosynthesis genetic loci in genera of the Burkholderiales, which are paradoxically distinguished from S. Typhi by encoding VexL, a predicted pectate lyase homolog. Biochemical analyses demonstrated that VexL is an unusual metal-independent endolyase with an acidic pH optimum that is specific for O-acetylated Vi antigen. A 1.22-A crystal structure of the VexL-Vi antigen complex revealed features which distinguish common secreted catabolic pectate lyases from periplasmic VexL, which participates in cell-surface assembly. VexL possesses a right-handed parallel beta-superhelix, of which one face forms an electropositive glycan-binding groove with an extensive hydrogen bonding network that includes Vi antigen acetyl groups and confers substrate specificity. VexL provided a probe to interrogate conserved features of the ABC transporter-dependent export model. When introduced into S Typhi, VexL localized to the periplasm and degraded Vi antigen. In contrast, a cytosolic derivative had no effect unless export was disrupted. These data provide evidence that CPS assembled in ABC transporter-dependent systems is actually exposed to the periplasm during envelope translocation. Periplasmic depolymerase provides insight into ABC transporter-dependent secretion of bacterial capsular polysaccharides.,Liston SD, McMahon SA, Le Bas A, Suits MDL, Naismith JH, Whitfield C Proc Natl Acad Sci U S A. 2018 May 22;115(21):E4870-E4879. doi:, 10.1073/pnas.1801336115. Epub 2018 May 7. PMID:29735649 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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