title: Identification of essential loops and residues of glucosyltransferase V (GtrV) of Shigella flexneri.
abstract: Lipopolysaccharide (LPS), particularly the O-antigen component, is one of many virulence determinants necessary for Shigella flexneri pathogenesis. O-antigen modification is mediated by glucosyltransferase (gtr) genes encoded by temperate serotype-converting bacteriophages. The gtrV and gtrX genes encode the GtrV and GtrX glucosyltransferases, respectively. These are integral membrane proteins, which catalyze the transfer of a glucosyl residue via an alpha1,3 linkage to rhamnose II and rhamnose I of the O-antigen unit. This mediates conversion of S. flexneri serotype Y to serotype 5a and X, respectively. Essential regions in the topology of GtrV protein were identified by in vivo recombination and a PCR-mediated approach. A series of GtrX-GtrV and GtrV-GtrX chimeric proteins were constructed based on the fact that GtrV and GtrX share sequence similarity. Analysis of their respective serotype conversion abilities led to the identification of two important periplasmic loops: loops No 2 and No 10 located in the N- and C-termini, respectively. Within these two loops, three conserved motifs were identified; two in loop No 2 and one in loop No 10. These conserved motifs contain acidic residues which were shown to be critical for GtrV function.
authors.affiliation: School of Biochemistry and Molecular Biology, Faculty of Science, The Australian National University, Canberra, Australia.
authors.forename: Haralambos
authors.initials: H
authors.lastname: Korres
authors.forename: Naresh K
authors.initials: NK
authors.lastname: Verma
mesh_terms: D000595:Amino Acid Sequence; D017124:Conserved Sequence; D005964:Glucosyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D019897:Periplasm / Q000378:metabolism; D016133:Polymerase Chain Reaction; D017434:Protein Structure, Tertiary; D011995:Recombination, Genetic; D017386:Sequence Homology, Amino Acid; D012763:Shigella flexneri / Q000201:enzymology*
chemical_list: D008565:Membrane Proteins; D005964:Glucosyltransferases; C487330:GtrV protein, Shigella flexneri