Involved in the maturation of the mitochondrial respiratory chain complex IV subunit MT-CO2/COX2. Thereby, may regulate early steps of complex IV assembly. Mitochondrial respiratory chain complex IV or cytochrome c oxidase is the component of the respiratory chain that catalyzes the transfer of electrons from intermembrane space cytochrome c to molecular oxygen in the matrix and as a consequence contributes to the proton gradient involved in mitochondrial ATP synthesis. May also be required for efficient formation of respiratory supercomplexes comprised of complexes III and IV. Found in a complex with TMEM177, COX20, MT-CO2/COX2, COX18, SCO1 and SCO2. Interacts with COA1, MT-CO2/COX2, SCO1, SCO2 and COX20. Interacts with COX20 in a MT-CO2/COX2- and COX18-dependent manner. Interacts with COX16. Belongs to the cytochrome c oxidase subunit 6B family.