Cytochrome c oxidase subunit II-like C-terminal (IPR002429)
Short name: CcO_II-like_C
Overlapping homologous superfamilies
- Cupredoxin (IPR008972)
- Cytochrome c oxidase subunit II-like C-terminal (IPR002429)
- Ba3-like heme-copper oxidase subunit II, C-terminal (IPR034214)
- Caa3-type Cytochrome c oxidase subunit II, cupredoxin domain (IPR034236)
- Cytochrome c oxidase subunit 2, C-terminal (IPR034210)
- Nitrous-oxide reductase, C-terminal (IPR034205)
- Ubiquinol oxidase subunit 2, cupredoxin domain (IPR034227)
Cytochrome c oxidase (EC:18.104.22.168) [PMID: 6307356, PMID: 8083153] is an oligomeric enzymatic complex which is a component of the respiratory chain and is involved in the transfer of electrons from cytochrome c to oxygen. In eukaryotes this enzyme complex is located in the mitochondrial inner membrane; in aerobic prokaryotes it is found in the plasma membrane. The number of polypeptides in the complex ranges from 3-4 (prokaryotes), up to 13(mammals). In Archaea, a cytochrome-c-type oxidase from Natronobacterium (cytochrome ba3) has been shown to consists of four subunits [PMID: 9428682].
Subunit 2 (CO II) transfers the electrons from cytochrome c to the catalytic subunit 1. It contains two adjacent transmembrane regions in its N terminus and the major part of the protein is exposed to the periplasmic or to the mitochondrial intermembrane space, respectively. CO II provides the substrate-binding site and contains a copper centre called Cu(A), probably the primary acceptor in cytochrome c oxidase. An exception is the corresponding subunit of the cbb3-type oxidase which lacks the copper A redox-centre. Several bacterial CO II have a C-terminal extension that contains a covalently bound haem c.
It has been shown [PMID: 1324168, PMID: 1324835] that nitrous oxide reductase (gene nosZ) of Pseudomonas has sequence similarity in its C terminus to CO II. This enzyme is part of the bacterial respiratory system which is activated under anaerobic conditions in the presence of nitrate or nitrous oxide. NosZ is a periplasmic homodimer that contains a dinuclear copper centre, probably located in a 3-dimensional fold similar to the cupredoxin-like fold that has been suggested for the copper-binding site of CO II [PMID: 1324168].