Required for the assembly of the mitochondrial respiratory chain complex IV (CIV), also known as cytochrome c oxidase (PubMed:29355485, PubMed:29381136, PubMed:33169484). Promotes the insertion of copper into the active site of cytochrome c oxidase subunit II (MT-CO2/COX2) (PubMed:29355485, PubMed:29381136). Interacts specifically with newly synthesized MT-CO2/COX and its copper center-forming metallochaperones SCO1, SCO2 and COA6 (PubMed:29381136). Probably facilitates MT-CO2/COX2 association with the MITRAC assembly intermediate containing MT-CO1/COX1, thereby participating in merging the MT-CO1/COX1 and MT-CO2/COX2 assembly lines (PubMed:29381136). Associates with the MITRAC complex (PubMed:29381136). Interacts with MT-CO2/COX; specifically interacts with newly synthesized MT-CO2/COX (PubMed:29355485, PubMed:29381136). Interacts with SCO1, SCO2 and COA6 (PubMed:29381136). Widely expressed. Expressed at higher level in skeletal muscle, heart and liver. The disease is caused by variants affecting the gene represented in this entry. No COX16 mutations have been detected in patients with cytochrome c oxidase (COX) deficiency. Belongs to the COX16 family.