Mitochondrial membrane insertase required for the translocation of the C-terminus of cytochrome c oxidase subunit II (MT-CO2/COX2) across the mitochondrial inner membrane. Plays a role in MT-CO2/COX2 maturation following the COX20-mediated stabilization of newly synthesized MT-CO2/COX2 protein and before the action of the metallochaperones SCO1/2. Essential for the assembly and stability of the mitochondrial respiratory chain complex IV (also known as cytochrome c oxidase). Found in a complex with TMEM177, COA6, MT-CO2/COX2, COX20, SCO1 and SCO2 (PubMed:29154948). Interacts transiently with MT-CO2/COX2 during its maturation (PubMed:28330871). Interacts with COX20 in a MT-CO2/COX2-dependent manner (PubMed:28330871). Belongs to the OXA1/ALB3/YidC family. Contaminating sequence. Potential poly-A sequence.