InterPro domain: IPR014241

This entry represents the bacterial-type cytochrome c oxidase subunit I (CtaD, CoxA, CaaA). Cytochrome c oxidase is the component of the respiratory chain that catalyses the reduction of oxygen to water. Subunits I, II and III form the functional core of the enzyme complex. Subunit I is the catalytic subunit of the enzyme. Electrons originating in cytochrome c are transferred via the copper A centre of subunit II and haem A of subunit I to the bimetallic centre formed by haem A3 and copper B. This cytochrome c oxidase shows proton pump activity across the membrane in addition to the electron transfer activity. In the bacilli an apparent split (paralogism) has created a sister clade ( IPR014233 ) encoding subunits (QoxA) of the aa3-type quinone oxidase complex which reacts directly with quinones, bypassing the interaction with soluble cytochrome c.