Homologous Superfamily

Cytochrome c oxidase subunit III-like superfamily (IPR035973)

Short name: Cyt_c_oxidase_su3-like_sf

Overlapping entries


Cytochrome c oxidase (EC: is the terminal enzyme of the respiratory chain of mitochondria and many aerobic bacteria. It catalyses the transfer of electrons from reduced cytochrome c to molecular oxygen:

4 cytochrome c+2 + 4 H+ + O2 --> 4 cytochrome c+3 + 2 H2O

This reaction is coupled to the pumping of four additional protons across the mitochondrial or bacterial membrane [PMID: 10563795, PMID: 16598262].

Cytochrome c oxidase is an oligomeric enzymatic complex that is located in the mitochondrial inner membrane of eukaryotes and in the plasma membrane of aerobic prokaryotes. The core structure of prokaryotic and eukaryotic cytochrome c oxidase contains three common subunits, I, II and III. In prokaryotes, subunits I and III can be fused and a fourth subunit is sometimes found, whereas in eukaryotes there are a variable number of additional small polypeptidic subunits [PMID: 8383670]. The functional role of subunit III is not yet understood.

As the bacterial respiratory systems are branched, they have a number of distinct terminal oxidases, rather than the single cytochrome c oxidase present in the eukaryotic mitochondrial systems. Even though the cytochrome o complex oxidises quinol (ubiquinol) and does not catalyse the oxidation of reduced cytochrome c, they belong to the same haem-copper oxidase superfamily as cytochrome c oxidases. Members of this family share sequence similarities in all three core subunits: subunit I is the most conserved subunit, whereas subunit II is the least conserved [PMID: 1316894, PMID: 2162835, PMID: 8083153].

This entry represents a structural domain found in cytochrome c and ubiquinol oxidase subunit III. The overall structure of these enzymes is similar [PMID: 11017202].

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0015002 heme-copper terminal oxidase activity

Cellular Component

GO:0016020 membrane

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.