title: The topology of the anchor subunit of dimethyl sulfoxide reductase of Escherichia coli.
abstract: The terminal electron transfer enzyme Me2SO reductase of Escherichia coli is a heterotrimeric enzyme composed of a membrane extrinsic catalytic dimer (DmsAB) and a membrane intrinsic polytopic anchor subunit (DmsC). The topology of DmsC has been studied using phoA (alkaline phosphatase) and blaM (beta-lactamase) gene fusions. The results of analyzing the properties of proteins produced by the fusions suggests a structure with eight transmembrane helices. Both the amino and carboxyl termini are exposed to the periplasm. The entire DmsC polypeptide is necessary to anchor DmsAB to the membrane as fusions with truncated DmsC were not functional and soluble DmsAB accumulated in the cytoplasm. A dmsC-phoA fusion in the termination codon of dmsC generated a chimeric enzyme with functional Me2SO reductase and alkaline phosphatase activity. Quantitation of the minimal inhibitory concentration of ampicillin for the dmsC-blaM fusions indicated that different transmembrane helices had differing signal sequence activity.
authors.affiliation: Department of Biochemistry, University of Alberta, Edmonton, Canada.
authors.forename: J H
authors.initials: JH
authors.lastname: Weiner
authors.forename: G
authors.initials: G
authors.lastname: Shaw
authors.forename: R J
authors.initials: RJ
authors.lastname: Turner
authors.forename: C A
authors.initials: CA
authors.lastname: Trieber
mesh_terms: D000469:Alkaline Phosphatase / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D000595:Amino Acid Sequence; D001483:Base Sequence; D015153:Blotting, Western; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D005798:Genes, Bacterial; D007506:Iron-Sulfur Proteins; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D010088:Oxidoreductases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D010957:Plasmids; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000302:isolation & purification; D001618:beta-Lactamases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification
chemical_list: D007506:Iron-Sulfur Proteins; D046911:Macromolecular Substances; D009838:Oligodeoxyribonucleotides; D011993:Recombinant Fusion Proteins; D010088:Oxidoreductases; C045664:dimethyl sulfoxide reductase; D000469:Alkaline Phosphatase; D001618:beta-Lactamases