This protein is one of the nuclear-coded polypeptide chains of cytochrome c oxidase, the terminal oxidase in mitochondrial electron transport. Sweet potato cytochrome C oxidase consists of at least seven different polypeptides species, subunits I, II, III, IV, Va, Vb, and Vc in order of MW. This precursor was imported into isolated sweet potato tuberous root mitochondria without any significant processing, the import being dependent on membrane potential. Belongs to the cytochrome c oxidase subunit 5C family.