title: Cyanide-insensitive quinol oxidase (CIO) from Gluconobacter oxydans is a unique terminal oxidase subfamily of cytochrome bd.
abstract: Cyanide-insensitive terminal quinol oxidase (CIO) is a subfamily of cytochrome bd present in bacterial respiratory chain. We purified CIO from the Gluconobacter oxydans membranes and characterized its properties. The air-oxidized CIO showed some or weak peaks of reduced haemes b and of oxygenated and ferric haeme d, differing from cytochrome bd. CO- and NO-binding difference spectra suggested that haeme d serves as the ligand-binding site of CIO. Notably, the purified CIO showed an extraordinary high ubiquinol-1 oxidase activity with the pH optimum of pH 5-6. The apparent Vmax value of CIO was 17-fold higher than that of G. oxydans cytochrome bo3. In addition, compared with Escherichia coli cytochrome bd, the quinol oxidase activity of CIO was much more resistant to cyanide, but sensitive to azide. The Km value for O2 of CIO was 7- to 10-fold larger than that of G. oxydans cytochrome bo3 or E. coli cytochrome bd. Our results suggest that CIO has unique features attributable to the structure and properties of the O2-binding site, and thus forms a new sub-group distinct from cytochrome bd. Furthermore, CIO of acetic acid bacteria may play some specific role for rapid oxidation of substrates under acidic growth conditions.
authors.affiliation: Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University, Yamaguchi 753-8515, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Miura
authors.forename: Tatsushi
authors.initials: T
authors.lastname: Mogi
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Ano
authors.forename: Catharina T
authors.initials: CT
authors.lastname: Migita
authors.forename: Minenosuke
authors.initials: M
authors.lastname: Matsutani
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Yakushi
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Kita
authors.forename: Kazunobu
authors.initials: K
authors.lastname: Matsushita
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D003486:Cyanides / Q000737:chemistry / Q000378:metabolism*; D003573:Cytochrome b Group; D003580:Cytochromes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004579:Electron Transport; D045222:Electron Transport Chain Complex Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020600:Gluconobacter oxydans / Q000201:enzymology* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D003486:Cyanides; D003573:Cytochrome b Group; D003580:Cytochromes; D045222:Electron Transport Chain Complex Proteins; D029968:Escherichia coli Proteins; D010088:Oxidoreductases; C020094:duroquinol oxidase; C040077:cytochrome bd terminal oxidase complex, E coli; D010100:Oxygen
keywords: Gluconobacter oxydans; cyanide-insensitive quinol oxidase (CIO); cytochrome bd; cytochrome bo3; respiratory chain