title: Probing a role of subunit IV of the Escherichia coli bo-type ubiquinol oxidase by deletion and cross-linking analyses.
abstract: Subunit IV of the Escherichia coli bo-type ubiquinol oxidase is a 12-kDa membrane protein encoded by the cyoD gene and is conserved in the bacterial heme-copper terminal oxidases. To probe the functional role of subunit IV, we carried out deletion analysis and chemical cross-linking experiments with a homobifunctional and cleavable reagent. Spectroscopic properties of the mutant oxidases suggest that the C-terminal two-third (Val45 to His109) containing helices II and III is essential for the functional expression of the oxidase complex and for the CuB binding to the heme-copper binuclear center in subunit I. Cross-linking studies indicate that subunit IV is in close vicinity to subunit III. Based on these observations, we propose that subunit IV is present in a cleft formed by subunits I and III and assists the CuB binding to subunit I during biosynthesis or assembly of the oxidase complex.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, the University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Saiki
authors.forename: H
authors.initials: H
authors.lastname: Nakamura
authors.forename: T
authors.initials: T
authors.lastname: Mogi
authors.forename: Y
authors.initials: Y
authors.lastname: Anraku
mesh_terms: D000595:Amino Acid Sequence; D002384:Catalysis; D003432:Cross-Linking Reagents; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D011994:Recombinant Proteins; D017384:Sequence Deletion; D013329:Structure-Activity Relationship
chemical_list: D003432:Cross-Linking Reagents; D046911:Macromolecular Substances; D011994:Recombinant Proteins; C038862:cytochrome o oxidase; D003576:Electron Transport Complex IV