title: Subunit CydX of Escherichia coli cytochrome bd ubiquinol oxidase is essential for assembly and stability of the di-heme active site.
abstract: Cytochrome bd ubiquinol oxidase uses the electron transport from ubiquinol to oxygen to establish a proton gradient across the membrane. The enzyme complex consists of subunits CydA and B and contains two b- and one d-type hemes as cofactors. Recently, it was proposed that a third subunit named CydX is essential for the function of the complex. Here, we show that CydX is indeed a subunit of purified Escherichia coli cytochrome bd oxidase and that the small protein is needed either for the assembly or the stability of the active site di-heme center and, thus, is essential for oxidase activity.
authors.affiliation: Albert-Ludwigs-Universität Freiburg, Institut für Biochemie, Albertstr. 21, 79104 Freiburg i. Br., Germany.
authors.forename: Jo
authors.initials: J
authors.lastname: Hoeser
authors.affiliation: Department of Biochemistry, University of Illinois, 600 S Goodwin Ave, A320 CLSL, MC-712, Urbana, IL 61801, USA.
authors.forename: Sangjin
authors.initials: S
authors.lastname: Hong
authors.affiliation: Albert-Ludwigs-Universität Freiburg, Institut für Biochemie, Albertstr. 21, 79104 Freiburg i. Br., Germany.
authors.forename: Gerfried
authors.initials: G
authors.lastname: Gehmann
authors.affiliation: Department of Biochemistry, University of Illinois, 600 S Goodwin Ave, A320 CLSL, MC-712, Urbana, IL 61801, USA.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Gennis
authors.affiliation: Albert-Ludwigs-Universität Freiburg, Institut für Biochemie, Albertstr. 21, 79104 Freiburg i. Br., Germany. Electronic address: friedrich@bio.chemie.uni-freiburg.de.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Friedrich
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain; D002846:Chromatography, Affinity; D003573:Cytochrome b Group; D003580:Cytochromes / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D045222:Electron Transport Chain Complex Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D004795:Enzyme Stability; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D055503:Protein Multimerization; D021122:Protein Subunits / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification
chemical_list: D003573:Cytochrome b Group; D003580:Cytochromes; D045222:Electron Transport Chain Complex Proteins; D029968:Escherichia coli Proteins; D021122:Protein Subunits; D010088:Oxidoreductases; C040077:cytochrome bd terminal oxidase complex, E coli
keywords: CydAB; CydX; Escherichia coli; UV/vis difference spectroscopy; Ubiquinol cytochrome bd oxidase