InterPro domain: IPR035908

F-ATPases (also known as ATP synthases, F1F0-ATPase, or H(+)-transporting two-sector ATPase) ( 7.1.2.2 ) are composed of two linked complexes: the F1 ATPase complex is the catalytic core and is composed of 5 subunits (alpha, beta, gamma, delta, epsilon), while the F0 ATPase complex is the membrane-embedded proton channel that is composed of at least 3 subunits (A-C), with additional subunits in mitochondria. Both the F1 and F0 complexes are rotary motors that are coupled back-to-back. In the F1 complex, the central gamma subunit forms the rotor inside the cylinder made of the alpha(3)beta(3) subunits, while in the F0 complex, the ring-shaped C subunits forms the rotor. The two rotors rotate in opposite directions, but the F0 rotor is usually stronger, using the force from the proton gradient to push the F1 rotor in reverse in order to drive ATP synthesis [ 1 ]. These ATPases can also work in reverse in bacteria, hydrolysing ATP to create a proton gradient.

This superfamily represents the up-and-down bundle of four transmembrane helices structure found in the F0 complex subunit A. This subunit is a key component of the proton channel, and may play a direct role in the translocation of protons across the membrane. Catalysis in the F1 complex depends upon the rotation of the central stalk and F0 c-ring, which in turn is driven by the flux of protons through the membrane via the interface between the F0 c-ring and subunit A. The peripheral stalk links subunit A to the external surface of the F1 domain, and is thought to act as a stator to counter the tendency of subunit A and the F1 alpha(3)beta(3) catalytic portion to rotate with the central rotary element[ 2 ].

1. Resolution of distinct rotational substeps by submillisecond kinetic analysis of F1-ATPase. Nature 410, 898-904
2. Structure of the F1-binding domain of the stator of bovine F1Fo-ATPase and how it binds an alpha-subunit. J. Mol. Biol. 351, 824-38