The F-ATPase is found in bacterial plasma membranes, mitochondrial inner membranes and in chloroplast thylakoid membranes. It has also been found in the archaea Methanosarcina barkeri. It uses a proton gradient to drive ATP synthesis and hydrolyzes ATP to build the proton gradient. The mitochondrial extrinsic membrane domain, F1, is composed of alpha, beta, gamma, delta and epsilon subunits with a stoichiometry of 3:3:1:1:1. The alpha subunit of the F1 ATP synthase can bind nucleotides, but is non-catalytic. Alpha and beta subunits form the globular catalytic moiety, a hexameric ring of alternating alpha and beta subunits. Gamma, delta and epsilon subunits form a stalk, connecting F1 to F0, the integral membrane proton-translocating domain.