There are at least 26 known assembly/ancillary proteins with unknown numbers of other proteins, with ten associated with Complex IV deficiency: CEP89, COX14, COX20, COA3, COA7, COA8, PET100, PET117, TACO1, and SURF1[75]. Here, PET117 is linked to hyperinsulinemic hypoglycemia, familial, 4.