Proposed subunit of cytochrome c oxidase (COX, complex IV), which is the terminal component of the mitochondrial respiratory chain that catalyzes the reduction of oxygen to water. May be involved in cytochrome c oxidase activity. May play a role in the assembly of respiratory supercomplexes. . This is the function of HIGD2A (HIG1 hypoxia inducible domain family member 2A, Ensembl gene identifier ENSG00000146066).