title: Bacteriophage-encoded glucosyltransferase GtrII of Shigella flexneri: membrane topology and identification of critical residues.
abstract: The Shigella flexneri serotypes differ in the nature of their O-antigens. The addition of glucosyl or O-acetyl groups to the common backbone repeat units gives rise to the different serotypes. GtrII glucosylates rhamnose III of the O-antigen repeat unit, thus converting serotype Y (which has no modifications to the basic O-antigen repeat unit) into serotype 2a, the most prevalent serotype. In the present study, the topology of GtrII has been determined. GtrII has nine transmembrane helices, a re-entrant loop and three large periplasmic regions. Four critical residues (Glu40, Phe414, Cys435 and Lys478) were identified in two of the periplasmic regions. Despite the lack of sequence similarity between GtrII and the Gtrs from other serotypes, three of the critical residues identified are conserved in the remaining Gtrs. This is consistent with some degree of mechanistic conservation in this functionally related group of proteins.
authors.affiliation: School of Biochemistry and Molecular Biology, Faculty of Science Building 41, The Australian National University, Canberra ACT 0200, Australia.
authors.forename: Adele M
authors.initials: AM
authors.lastname: Lehane
authors.forename: Haralambos
authors.initials: H
authors.lastname: Korres
authors.forename: Naresh K
authors.initials: NK
authors.lastname: Verma
mesh_terms: D001435:Bacteriophages / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics / Q000821:virology; D015870:Gene Expression; D005964:Glucosyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D009154:Mutation; D019897:Periplasm / Q000201:enzymology; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012703:Serotyping; D012763:Shigella flexneri / Q000201:enzymology* / Q000235:genetics
chemical_list: D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; D005964:Glucosyltransferases