Mitochondrial ATP synthase is composed of two multi-subunit complexes that utilize an inner membrane electrochemical gradient to catalyze the synthesis of ATP during oxidative phosphorylation. The two multi-subunit complexes are designated F1 and F0, the former of which comprises the soluble catalytic core and the latter of which comprises the membrane-spanning proton channel of ATP synthase. ATP8, also known as MT-ATP8, ATPASE8 or MTATP8, is a 68 amino acid single-pass membrane protein that localizes to mitochondria and functions as a minor subunit of the F0 complex. The gene encoding ATP8 maps to the mitochondrial chromosome and may be involved in the pathogenesis of multiple sclerosis.