PET117 (PET117 Cytochrome C Oxidase Chaperone) is located on human chromosome 20p11.23. PET117 protein is ubiquitously expressed in duodenum, stomach, testis and other tissues. PET117 is associated with some diseases, including Mitochondrial Complex Iv Deficiency and 2-Aminoadipic 2-Oxoadipic Aciduria. Pet117 is shown to reside in the mitochondrial matrix, where it is associated with the inner membrane. Pet117 functions at the later maturation stages of the core CcO subunit Cox1 that precede Cox1 hemylation. Pet117 also physically interacts with Cox15 and specifically mediates the stability of Cox15 oligomeric complexes. Pet117 mediates coupling of heme a synthesis to the CcO assembly process in eukaryotes.