Key component of the proton channel; it plays a direct role in the translocation of protons across the membrane. 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. Induced by a decrease in external pH from 7.5 to 5.7. Belongs to the ATPase A chain family.