This gene encodes a subunit of the ubiquinol-cytochrome c oxidoreductase complex, which consists of one mitochondrial-encoded and 10 nuclear-encoded subunits. The protein encoded by this gene binds ubiquinone and participates in the transfer of electrons when ubiquinone is bound. This protein plays an important role in hypoxia-induced angiogenesis through mitochondrial reactive oxygen species-mediated signaling. Mutations in this gene are associated with mitochondrial complex III deficiency. Alternatively spliced transcript variants have been found for this gene. Related pseudogenes have been identified on chromosomes 1, 5 and X.