Cytochrome c oxidase assembly protein is essential for the assembly of functional cytochrome oxidase protein. In eukaryotes it is an integral protein of the mitochondrial inner membrane. Cox11 is essential for the insertion of Cu(I) ions to form the CuB site. This is essential for the stability of other structures in subunit I, for example haems a and a3, and the magnesium/manganese centre. Cox11 is probably only required in sub-stoichiometric amounts relative to the structural units [1]. The C terminal region of the protein is known to form a dimer. Each monomer coordinates one Cu(I) ion via three conserved cysteine residues (111, 208 and 210) in Saccharomyces cerevisiae (Swiss:P19516). Met 224 is also thought to play a role in copper transfer or stabilising the copper site [2].

1: Cox11p is required for stable formation of the Cu(B) and magnesium centers of cytochrome c oxidase. Hiser L, Di Valentin M, Hamer AG, Hosler JP; J Biol Chem 2000;275:619-623. PMID:10617659

2: Yeast Cox11, a protein essential for cytochrome c oxidase assembly, is a Cu(I) binding protein. Carr HS, George GN, Winge DR; J Biol Chem 2002;277:31237-31242. PMID:12063264