title: Complete nucleotide sequence and molecular characterization of ViaB region encoding Vi antigen in Salmonella typhi.
abstract: Plasmid pGBM124, which contains a 14-kb Salmonella typhi chromosomal DNA fragment capable of producing the Vi antigen in Escherichia coli HB101 and ViaB-deleted S. typhi GIFU 10007-3, was studied. We determined the complete nucleotide sequence of this fragment and found 11 open reading frames. Mutagenesis, subcloning, and complementation analysis showed that three genes (vipA, vipB, and vipC) are involved in biosynthesis of the Vi polysaccharide. The putative primary amino acid sequence suggests that both vipA and vipB encode the NAD- or NADP-dependent enzymes to synthesize the nucleotide sugar for the Vi polysaccharide. Five genes (vexA, vexB, vexC, vexD, and vexE) may be involved in translocation of the Vi polysaccharide. Proteins VexA, VexB, VexC, and VexD had moderate similarities to components of group II capsule transporters, and the VexC protein had a putative ATP-binding site. These data indicate that the transport system for the Vi polysaccharide belongs to the ATP-binding cassette transporters. By using the isogenic Vi+ and Vi- strains constructed in this study, we reconfirmed that the Vi antigen is necessary for the serum resistance of S. typhi.
authors.affiliation: Department of Microbiology, Gifu University School of Medicine, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Hashimoto
authors.forename: N
authors.initials: N
authors.lastname: Li
authors.forename: H
authors.initials: H
authors.lastname: Yokoyama
authors.forename: T
authors.initials: T
authors.lastname: Ezaki
mesh_terms: D000372:Agglutination Tests; D000595:Amino Acid Sequence; D000942:Antigens, Bacterial / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics*; D001345:Autoradiography; D001483:Base Sequence; D002876:Chromosomes, Bacterial; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D005798:Genes, Bacterial; D006801:Humans; D005779:Immunodiffusion; D008715:Methionine / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family; D016254:Mutagenesis, Insertional; D016366:Open Reading Frames; D011135:Polysaccharides, Bacterial; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000032:analysis / Q000096:biosynthesis; D015183:Restriction Mapping; D012485:Salmonella typhi / Q000235:genetics* / Q000378:metabolism*; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D013462:Sulfur Radioisotopes
chemical_list: D000942:Antigens, Bacterial; D004269:DNA, Bacterial; D011135:Polysaccharides, Bacterial; D011993:Recombinant Fusion Proteins; D013462:Sulfur Radioisotopes; D008715:Methionine