COQ10 is a hydrophobic protein located in the inner membrane of mitochondria that binds coenzyme Q (CoQ), also called ubiquinone, which is an essential electron carrier of the respiratory chain. Deletion of the gene encoding COQ10p (COQ10 or YOL008W) in Saccharomyces cerevisiae results in respiratory defect because of the inability to oxidize NADH and succinate. COQ10 may function in the delivery of CoQ (Q6 in budding yeast) to its proper location for electron transport [, ]. The human homologue, called Q-binding protein COQ10 homologue A (COQ10A), is able to fully complement for the absence of COQ10 in fission yeast. Human COQ10A also has a splice variant COQ10B []. COQ10 belongs to the SRPBCC (START/RHO_alpha_C/PITP/Bet_v1/CoxG/CalC) domain superfamily of proteins that bind hydrophobic ligands. SRPBCC domains have a deep hydrophobic ligand-binding pocket and they bind diverse ligands [, ].
