Cytochrome c oxidase, subunit Vb is a subunit of mitochondrial cytochrome c oxidase complex.
Cytochrome c oxidase (EC 184.108.40.206) is an oligomeric enzymatic complex which is a component of the respiratory chain complex 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.
In eukaryotes, in addition to the three large subunits, I, II and III, that form the catalytic centre of the enzyme complex, there are a variable number of small polypeptidic subunits. One of these subunits is known as Vb in mammals, V in Dictyostelium discoideum (Slime mold) and IV in yeast, binds a zinc atom. The sequence of subunit Vb is well conserved and includes three conserved cysteines that coordinate the zinc ion. Two of these cysteines are clustered in the C-terminal section of the subunit.