Produces ATP from ADP in the presence of a proton gradient across the membrane. The alpha chain is a regulatory subunit. ATP + 4 H(+)(in) + H2O = ADP + 5 H(+)(out) + phosphate F-type ATPases have 2 components, CF(1) - the catalytic core - and CF(0) - the membrane proton channel. CF(1) has five subunits: alpha(3), beta(3), gamma(1), delta(1), epsilon(1). CF(0) has three main subunits: a(1), b(2) and c(9-12). The alpha and beta chains form an alternating ring which encloses part of the gamma chain. CF(1) is attached to CF(0) by a central stalk formed by the gamma and epsilon chains, while a peripheral stalk is formed by the delta and b chains. Detected in both the small cell variant (SCV) and in the large cell variant (LCV) stage (at protein level). LCVs are more metabolically active than SCVs. Belongs to the ATPase alpha/beta chains family.