title: Cytochrome oxidase evolved by tinkering with denitrification enzymes.
abstract: The cytochrome bc complex which is encoded by the fixNOPQ operon in Bradyrhizobium japonicum, is the most distant member of the haem-copper cytochrome oxidase family. We have found that its major subunit, FixN, is homologous to the NorB subunit of nitric oxide reductase in a purple bacterium. A second evolutionary link between cytochrome oxidases and denitrification enzymes is the presence of a similar binuclear copper site in cytochrome aa3 (the mitochondrial oxidase) and nitrous oxide reductase. This centre was probably acquired by a primitive FixN-type oxidase, leading to the evolution of the mitochondrial-type oxidase. These links suggest that the oxygen-reducing respiratory chain developed from the anaerobic, denitrifying respiratory system.
authors.affiliation: European Molecular Biology Laboratory, Heidelberg, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Saraste
authors.forename: J
authors.initials: J
authors.lastname: Castresana
mesh_terms: D000595:Amino Acid Sequence; D005075:Biological Evolution; D003300:Copper; D003576:Electron Transport Complex IV / Q000378:metabolism*; D008969:Molecular Sequence Data; D009573:Nitrites / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism
chemical_list: D009573:Nitrites; D003300:Copper; D010088:Oxidoreductases; C034747:nitric-oxide reductase; D003576:Electron Transport Complex IV