Required for efficient assembly of cytochrome c oxidase in the mitochondrial inner membrane. Involved in a step coupling MSS51-dependent cotranslational insertion of COX1 to the addition of its heme A and copper B cofactors. Interacts with COX1, COX14, MSS51 and SHY1. Present with 1680 molecules/cell in log phase SD medium. Belongs to the COA1 family.