title: Heme-copper terminal oxidase using both cytochrome c and ubiquinol as electron donors.
abstract: The cytochrome c oxidase Cox2 has been purified from native membranes of the hyperthermophilic eubacterium Aquifex aeolicus. It is a cytochrome ba(3) oxidase belonging to the family B of the heme-copper containing terminal oxidases. It consists of three subunits, subunit I (CoxA2, 63.9 kDa), subunit II (CoxB2, 16.8 kDa), and an additional subunit IIa of 5.2 kDa. Surprisingly it is able to oxidize both reduced cytochrome c and ubiquinol in a cyanide sensitive manner. Cox2 is part of a respiratory chain supercomplex. This supercomplex contains the fully assembled cytochrome bc(1) complex and Cox2. Although direct ubiquinol oxidation by Cox2 conserves less energy than ubiquinol oxidation by the cytochrome bc(1) complex followed by cytochrome c oxidation by a cytochrome c oxidase, ubiquinol oxidation by Cox2 is of advantage when all ubiquinone would be completely reduced to ubiquinol, e.g., by the sulfidequinone oxidoreductase, because the cytochrome bc(1) complex requires the presence of ubiquinone to function according to the Q-cycle mechanism. In the case that all ubiquinone has been reduced to ubiquinol its reoxidation by Cox2 will enable the cytochrome bc(1) complex to resume working.
authors.affiliation: Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, D-60438 Frankfurt, Germany.
authors.forename: Ye
authors.initials: Y
authors.lastname: Gao
authors.forename: Björn
authors.initials: B
authors.lastname: Meyer
authors.forename: Lucie
authors.initials: L
authors.lastname: Sokolova
authors.forename: Klaus
authors.initials: K
authors.lastname: Zwicker
authors.forename: Michael
authors.initials: M
authors.lastname: Karas
authors.forename: Bernd
authors.initials: B
authors.lastname: Brutschy
authors.forename: Guohong
authors.initials: G
authors.lastname: Peng
authors.forename: Hartmut
authors.initials: H
authors.lastname: Michel
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D052837:Chemoautotrophic Growth; D003300:Copper; D003486:Cyanides / Q000494:pharmacology; D045304:Cytochromes c / Q000378:metabolism*; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000037:antagonists & inhibitors / Q000145:classification / Q000302:isolation & purification / Q000378:metabolism*; D004583:Electrons; D004734:Energy Metabolism; D006418:Heme; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes; D010084:Oxidation-Reduction; D021122:Protein Subunits; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014451:Ubiquinone / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D003486:Cyanides; D009097:Multienzyme Complexes; D021122:Protein Subunits; D014451:Ubiquinone; D006418:Heme; D003300:Copper; D045304:Cytochromes c; D003576:Electron Transport Complex IV; C003741:ubiquinol