title: Topological investigation of glucosyltransferase V in Shigella flexneri using the substituted cysteine accessibility method.
abstract: Modification of the lipopolysaccharide O-antigen of Shigella converts the serotype, which is significant as acquired immune responses are serotype specific. Glucosyltransferases (Gtrs) modify the O-antigen by the addition of glucosyl-groups; however the precise mechanism of O-antigen modification is not fully understood. This study aims to substantiate inferences made on the GtrV topological structure using the substituted cysteine accessibility method (SCAM). Twenty-one amino acid residues were tested to clarify three features of GtrV: the extramembrane regions, a proposed reentrant loop, and a membrane border region. Overall, the results agreed with a previous topology proposed for GtrV. The topology of GtrV consists of 11 extramembrane regions with a cytoplasmic N-terminus, periplasmic C-terminus and 9 transmembrane (TM) helices. The existence of a reentrant loop between TM helices IV and V was verified, and the cytoplasmic membrane border region of TM helix II was examined in depth.
authors.affiliation: Division of Biomedical Science and Biochemistry, Research School of Biology, The Australian National University, Canberra, Australian Capital Territory 0200, Australia.
authors.forename: Anthony D
authors.initials: AD
authors.lastname: Rusden
authors.forename: David P
authors.initials: DP
authors.lastname: Stephenson
authors.forename: Naresh K
authors.initials: NK
authors.lastname: Verma
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D005964:Glucosyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017434:Protein Structure, Tertiary
chemical_list: D008565:Membrane Proteins; D005964:Glucosyltransferases; C487330:GtrV protein, Shigella flexneri; D003545:Cysteine