|PROSITE documentation PDOC00074|
Cytochrome c oxidase (EC 18.104.22.168)  is an oligomeric integral membrane protein complexes that catalyze the terminal step in the respiratory chain: they transfer electrons from cytochrome c or a quinol to oxygen. Some terminal oxidases generate a transmembrane proton gradient across the plasma membrane (prokaryotes) or the mitochondrial inner membrane (eukaryotes). The enzyme complex consists of 3-4 subunits (prokaryotes) up to 13 polypeptides (mammals) of which only the catalytic subunit (equivalent to mammalian subunit 1 (CO I)) is found in all heme-copper respiratory oxidases. The presence of a bimetallic center, formed by a high-spin heme (heme a3) and copper B, as well as a low-spin heme (heme a), both ligated to six conserved histidine residues near the outer side of four transmembrane spans within CO I is common to all family members [2,3,4].
In contrary to eukaryotes the respiratory chain of prokaryotes is branched to multiple terminal oxidases. The enzyme complexes vary in heme and copper composition, substrate type and substrate affinity. The different respiratory oxidases allow the cells to customize their respiratory systems according a variety of environmental growth conditions .
The crystal structure of the whole enzyme complexe have been solved . Subunit I contains 12 transmembrane helical segments and binds heme a and heme a3-copper B binuclear centre where molecular oxygen is reduced to water. (see <PDB:1OCZ; A>).
Recently also a component of an anaerobic respiratory chain has been found to contain the copper B binding signature of this family: nitric oxide reductase (NOR) exists in denitrifying species of Archae and Eubacteria.
Enzymes that belong to this family are:
As a signature pattern we used the copper-binding region. We also developed a profile that cover the whole subunit I.Note:
Cytochrome bd complexes do not belong to this family.Last update:
June 2004 / Text revised; profile added.
PROSITE methods (with tools and information) covered by this documentation:
|1||Authors||Garcia-Horsman J.A., Barquera B., Rumbley J., Ma J., Gennis R.B.|
|Source||J. Bacteriol. 176:5587-5600(1994).|
|2||Authors||Castresana J., Luebben M., Saraste M., Higgins D.G.|
|Title||Evolution of cytochrome oxidase, an enzyme older than atmospheric oxygen.|
|Source||EMBO J. 13:2516-2525(1994).|
|3||Authors||Capaldi R.A., Malatesta F., Darley-Usmar V.M.|
|Title||Structure of cytochrome c oxidase.|
|Source||Biochim. Biophys. Acta 726:135-148(1983).|
|4||Authors||Holm L., Saraste M., Wikstrom M.|
|Title||Structural models of the redox centres in cytochrome oxidase.|
|Source||EMBO J. 6:2819-2823(1987).|
|5||Authors||Yoshikawa S., Shinzawa-Itoh K., Nakashima R., Yaono R., Yamashita E., Inoue N., Yao M., Fei M.J., Libeu C.P., Mizushima T., Yamaguchi H., Tomizaki T., Tsukihara T.|
|Title||Redox-coupled crystal structural changes in bovine heart cytochrome c oxidase.|
|6||Authors||Saraste M., Castresana J.|
|Title||Cytochrome oxidase evolved by tinkering with denitrification enzymes.|
|Source||FEBS Lett. 341:1-4(1994).|