InterPro domain: IPR026015

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.

The subunits called delta in bacterial and chloroplast ATPase, or OSCP (oligomycin sensitivity conferral protein) in mitochondrial ATPase (note that in mitochondria there is a different delta subunit, IPR001469 ). The OSCP/delta subunit appears to be part of the peripheral stalk that holds the F1 complex alpha3beta3 catalytic core stationary against the torque of the rotating central stalk, and links subunit A of the F0 complex with the F1 complex. In mitochondria, the peripheral stalk consists of OSCP, as well as F0 components F6, B and D. In bacteria and chloroplasts the peripheral stalks have different subunit compositions: delta and two copies of F0 component B (bacteria), or delta and F0 components B and B' (chloroplasts) [ 2 , 2 ].

This superfamily represents the N-terminal six alpha-helix bundle domain of the OSCP/delta subunit [ 3 ].

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
3. Solution structure of the N-terminal domain of the delta subunit of the E. coli ATPsynthase. Nat. Struct. Biol. 4, 198-201