Mitochondria have their own DNA (mtDNA, which is a 16.5-kb circular double-stranded DNA (dsDNA), encoding 13 polypeptides, 22 transfer RNA (tRNA), and two ribosomal RNA (rRNA). The 13 polypeptides are subunits of a series of large enzyme complexes located in the inner mitochondrial membrane necessary for ATP production via oxidative phosphorylation. The protein encoded by the MT-ATP6 gene belongs to the mitochondrial respiratory chain complex. The MT-ATP6 protein is one subunit of a large enzyme called ATP synthase, also known as complex V. This enzyme produces ATP from ADP in the presence of a proton gradient across the membrane which is generated by electron transport complexes of the respiratory chain. F-type ATPases have two components, CF(1) - the catalytic core - and CF(0) - the membrane proton channel, linked together by a central stalk and a peripheral stalk. CF(1) has five subunits: alpha(3), beta(3), gamma(1), delta(1), and epsilon(1). Complex V is responsible for the final step of oxidative phosphorylation, it allows protons to flow across CF(0) segment inside mitochondria, and then the CF(1) segment uses the energy created by this proton flow to convert a molecule called adenosine diphosphate (ADP) to ATP.