Required for cytochrome c complex (COX) IV assembly and function Protects COX assembly from oxidation-induced degradation, COX being the terminal component of the mitochondrial respiratory chain. In conditions of increased oxidative stress, the protein is stabilized, increasing its mature intramitochondrial form and thereby protecting COX from oxidatively induced degradation. N-terminal mitochondrial targeting sequence is cleaved from the mature protein once in the mitochondrion. In normal conditions, the cytoplasmic precursor protein is rapidly degraded by the ubiquitination-proteasome system (UPS). Oxidative stress induces protein stabilization and import into mitochondria where it protects COX from degradation. Belongs to the COA8 family. First thought to play a role in the regulation of apoptosis, mediating mitochondria-induced cell death in vascular smooth muscle cells through the release of cytochrome c (COX) from mitochondria and the activation of the caspase cascade. However, recent studies show that it is not directly involved in apoptosis regulation but in the protection of COX from oxidatively induced degradation.