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 extrinisic membrane domain of F-ATPases is composed of alpha, beta, gamma, delta, and epsilon (not present in bacteria) subunits with a stoichiometry of 3:3:1:1:1. Alpha and beta subunit form the globular catalytic moiety, a hexameric ring of alternating subunits. Gamma, delta and epsilon subunits form a stalk, connecting F1 to F0, the integral membrane proton translocating domain.
Jiyao W et al.(2023). "The conserved domain database in 2023.",