title: Gene fusions with beta-lactamase show that subunit I of the cytochrome bd quinol oxidase from E. coli has nine transmembrane helices with the O2 reactive site near the periplasmic surface.
abstract: The cytochrome bd quinol oxidase is a component of the respiratory chain of many prokaryotes. The enzyme contains two subunits, CydA and CydB, which were initially predicted based on the sequence of the Escherichia coli oxidase to have seven and eight transmembrane spans, respectively. More recently, the topological model of CydA was revised to predict nine transmembrane helices, based on additional sequence information from other organisms. In the current work, the topology of the E. coli oxidase was experimentally examined using beta-lactamase gene fusions. The results confirm the revised topology, which places the oxygen reactive site near the periplasmic surface.
authors.affiliation: Department of Biochemistry, University of Illinois, 600 South Mathews Street, Urbana, IL 61801, USA. jzhang1@uiuc.edu
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.forename: Blanca
authors.initials: B
authors.lastname: Barquera
authors.forename: Robert B
authors.initials: RB
authors.lastname: Gennis
mesh_terms: D019677:Artificial Gene Fusion / Q000379:methods*; D001483:Base Sequence; D001665:Binding Sites; D003573:Cytochrome b Group; D003580:Cytochromes / Q000737:chemistry* / Q000235:genetics; D045222:Electron Transport Chain Complex Proteins / Q000737:chemistry* / Q000235:genetics; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics; D008565:Membrane Proteins / Q000737:chemistry; D010088:Oxidoreductases / Q000737:chemistry* / Q000235:genetics; D010100:Oxygen / Q000378:metabolism*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D021122:Protein Subunits / Q000737:chemistry*; D011993:Recombinant Fusion Proteins; D001618:beta-Lactamases / Q000235:genetics
chemical_list: D003573:Cytochrome b Group; D003580:Cytochromes; D045222:Electron Transport Chain Complex Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D010088:Oxidoreductases; C040077:cytochrome bd terminal oxidase complex, E coli; D001618:beta-Lactamases; D010100:Oxygen