Liston SD, Ovchinnikova OG, Whitfield C Unique lipid anchor attaches Vi antigen capsule to the surface of Salmonella enterica serovar Typhi Proceedings of the National Academy of Sciences of the USA113(24) (2016)
6719-6724
Salmonellaenterica sv. Typhi
(previously named:Salmonellatyphi, NEW: Salmonella enterica ssp. enterica sv. Typhi)
(NCBI TaxID 90370,
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The structure was elucidated in this paper NCBI PubMed ID:27226298 Publication DOI:10.1073/pnas.1524665113 Journal NLM ID:7505876 Publisher: National Academy of Sciences Correspondence: cwhitfieuoguelph.ca Institutions: Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada, N1G2W1
Polysaccharide capsules are surface structures that are critical for the virulence of many Gram-negative pathogenic bacteria. Salmonella enterica serovar Typhi is the etiological agent of typhoid fever. It produces a capsular polysaccharide known as 'Vi antigen,' which is composed of nonstoichiometrically O-acetylated α-1,4-linked N-acetylgalactosaminuronic acid residues. This glycan is a component of currently available vaccines. The genetic locus for Vi antigen production is also present in soil bacteria belonging to the genus Achromobacter Vi antigen assembly follows a widespread general strategy with a characteristic glycan export step involving an ATP-binding cassette transporter. However, Vi antigen producers lack the enzymes that build the conserved terminal glycolipid characterizing other capsules using this method. Achromobacter species possess a Vi antigen-specific depolymerase enzyme missing in S enterica Typhi, and we exploited this enzyme to isolate acylated Vi antigen termini. Mass spectrometry analysis revealed a reducing terminal N-acetylhexosamine residue modified with two beta-hydroxyl acyl chains. This terminal structure resembles one half of lipid A, the hydrophobic portion of bacterial lipopolysaccharides. The VexE protein encoded in the Vi antigen biosynthesis locus shares similarity with LpxL, an acyltransferase from lipid A biosynthesis. In the absence of VexE, Vi antigen is produced, but its physical properties are altered, its export is impaired, and a Vi capsule structure is not assembled on the cell surface. The structure of the lipidated terminus dictates a unique assembly mechanism and has potential implications in pathogenesis and vaccine production.
Salmonella, Salmonella enterica, glycolipid, polysaccharide export, polysaccharide capsule, Vi antigen
Structure type: fragment of a bigger structure ; 1333.6659 [M-H]- Location inside paper: p.6721, fig.2B, fig.S4B Trivial name: Vi antigen Compound class: CPS
Methods: 13C NMR, DNA sequencing, SDS-PAGE, sugar analysis, acid hydrolysis, Western blotting, MS/MS, de-O-acetylation, genetic methods, HPLC, GPC, electron microscopy, CD, LC-MS, bioinformatic analysis, immunofluorescence microscopy, LC-ESI-QTOF MS/MS Biosynthesis and genetic data: genetic data Comments, role: lipid anchor of the Vi-antigen
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(previously named: Salmonella typhi, NEW: Salmonella enterica ssp. enterica sv. Typhi)
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