Cbb3-type cytochrome c oxidase is the component of the respiratory chain that catalyzes the reduction of oxygen to water. Subunits CcoN and CcoO form the functional core of the enzyme complex. Subunits CcoP and CcoQ may optionally bind to the core. CcoN is the catalytic subunit of the enzyme. Electrons originating in cytochrome c or a quinol are transferred to the bimetallic center formed by a high-spin heme and copper B. The complex also functions as a proton pump. 4 Fe(II)-[cytochrome c] + 8 H(+)(in) + O2 = 4 Fe(III)-[cytochrome c] + 4 H(+)(out) + 2 H2O Binds 1 copper ion per subunit, denoted as copper B. Binds 2 heme b groups per subunit, denoted as high- and low-spin. Energy metabolism; oxidative phosphorylation. Component of the cbb3-type cytochrome c oxidase at least composed of CcoN, CcoO, CcoQ and CcoP. Belongs to the heme-copper respiratory oxidase family.