Based on limited published evidence, COA5 is an assembly factor for cytochrome c oxidase (respiratory chain complex IV) localized to the mitochondrial inner membrane. COA5 stabilizes early complex IV assembly intermediates until displaced by the copper-delivery protein COX17 12. Recent functional studies demonstrate COA5 is essential for the early stage of complex IV biogenesis, specifically between MTCO1 maturation and MTCO2 incorporation 3. Pathogenic COA5 variants cause mitochondrial complex IV deficiency and neonatal hypertrophic cardiomyopathy 3. COA5 expression is modulated during cardiac ischemia/reperfusion injury 4.