Copper metallochaperone essential for the maturation of cytochrome c oxidase subunit II (MT-CO2/COX2). Not required for the synthesis of MT-CO2/COX2 but plays a crucial role in stabilizing MT-CO2/COX2 during its subsequent maturation. Involved in transporting copper to the Cu(A) site on MT-CO2/COX2 (By similarity). Plays an important role in the regulation of copper homeostasis by controlling the abundance and cell membrane localization of copper transporter CTR1 (PubMed:25683716, PubMed:28973536). Homodimer. Interacts with COA6. Found in a complex with TMEM177, COX20, COA6, MT-CO2/COX2, COX18 and SCO2. Interacts with TMEM177 in a COX20-dependent manner. Interacts with COX20 in a MT-CO2/COX2- and COX18-dependent manner. Interacts with COX16. Heart-specific and striated muscle-specific knockout mice exhibit a lethal phenotype due to a combined COX and copper deficiency that results in a dilated cardiomyopathy. Cardiac copper deficiency is caused by the mislocalization of copper transporter CTR1 to the cytoplasm (PubMed:28973536). Liver-specific knockout mice exhibit a lethal phenotype associated with profound hepatic COX and copper deficiencies. Hepatic copper deficiency is due to reduced localization of CTR1 at the cell membrane and an enhanced proteasomal degradation of CTR1 (PubMed:25683716). Belongs to the SCO1/2 family.