Rapid evolution of cytochrome c oxidase subunit II in camelids (Tylopoda, Camelidae).

Within cetartiodactyl species, both New and Old World camelids are uniquely adapted to the extremely hot and dry climates of African-Asian territories and to the high altitude cold and hypoxic environment of the whole Andean area. In order to investigate the potential association between these particular adaptations and mitochondrial aerobic energy production, we examined the camelid genes of cytochrome c oxidase subunits I, II, and III and the replacement of amino acids inferred. We found that all subunits had undergone a number of replacements in sites otherwise conserved in other cetartiodactyls. Changes of COXI and COXIII were mainly located in the transmembrane helices of proteins. For COXII, although most of the changes did not occur in sites directly involved in electron transfer, a shift of D by T at 115 position of Old World camelid might modify electrostatic interactions with cytochrome c. COXII also showed an increased relative evolutionary rate respect to other cetartiodactyls compared.