The cytochrome c oxidase (COX) family of proteins function as the final electron donor in the respiratory chain to drive a proton gradient across the inner mitochondrial membrane,ultimately resulting in the production of water and ATP. The mammalian COX apoenzyme is a dimer,with each monomer consisting of 13 subunits,some of which are mitochondrial and some of which are nuclear. COX7b (cytochrome c oxidase subunit VIIb polypeptide) and COX7b2 (cytochrome c oxidase subunit VIIb polypeptide 2) are 80 and 81 amino acid proteins,respectively,which exist as components of the COX complex,therefore playing an important role in electron transport. A rare polymorphism in the COX7b2 gene at codon 26 may be linked to nasopharyngeal carcinoma (NPC),the most common head and neck cancer in southern China.