title: The VC1777-VC1779 proteins are members of a sialic acid-specific subfamily of TRAP transporters (SiaPQM) and constitute the sole route of sialic acid uptake in the human pathogen Vibrio cholerae.
abstract: Sialic acids are nine-carbon amino sugars that are present on all mucous membranes and are often used by bacteria as nutrients. In pathogenic Vibrio the genes for sialic acid catabolism (SAC) are known to be important for host colonization, yet the route for sialic acid uptake is not proven. Vibrio cholerae contains a tripartite ATP-independent periplasmic (TRAP) transporter, SiaPQM (VC1777-VC1779), encoded by genes within the Vibrio pathogenicity island-2 (VPI-2), which are adjacent to the SAC genes nanA, nanE and nanK. We demonstrate a correlation of the occurrence of VPI-2 and the ability of Vibrio to grow on the common sialic acid N-acetylneuraminic acid (Neu5Ac), and that a V. cholerae N16961 mutant defective in vc1777, encoding the large membrane protein component of the TRAP transporter, SiaM, is unable to grow on Neu5Ac as the sole carbon source. Using the genome context and known structures of the SiaP protein component of the TRAP transporter, we define a subfamily of Neu5Ac-specific TRAP transporters, of which the vc1777-vc1779 genes are the only representatives in V. cholerae. A recent report has suggested that an entirely different TRAP transporter (VC1927-VC1929) is the Neu5Ac transporter in V. cholerae. Bioinformatics and genomic analysis suggest strongly that this is a C(4)-dicarboxylate-specific TRAP transporter, and indeed disruption of vc1929 results in a defect in growth on C(4)-dicarboxylates but not Neu5Ac. Together these data demonstrate unequivocally that the siaPQM-encoded TRAP transporter within VPI-2 is the sole sialic acid transporter in V. cholerae.
authors.affiliation: Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA.
authors.forename: Nityananda
authors.initials: N
authors.lastname: Chowdhury
authors.affiliation: Department of Biology (Area 10), University of York, York YO10 5YW, UK.
authors.forename: Jessica
authors.initials: J
authors.lastname: Norris
authors.affiliation: Department of Biology (Area 10), University of York, York YO10 5YW, UK.
authors.forename: Erin
authors.initials: E
authors.lastname: McAlister
authors.affiliation: Department of Biology (Area 10), University of York, York YO10 5YW, UK.
authors.forename: S Y Kathy
authors.initials: SYK
authors.lastname: Lau
authors.affiliation: Department of Biology (Area 10), University of York, York YO10 5YW, UK.
authors.forename: Gavin H
authors.initials: GH
authors.lastname: Thomas
authors.affiliation: Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA.
authors.forename: E Fidelma
authors.initials: EF
authors.lastname: Boyd
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D002771:Cholera / Q000382:microbiology*; D006801:Humans; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D005810:Multigene Family; D019158:N-Acetylneuraminic Acid / Q000378:metabolism*; D010802:Phylogeny; D014734:Vibrio cholerae / Q000145:classification / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D019158:N-Acetylneuraminic Acid