Structural domains comprising this superfamily share the structure of the C-terminal domain of both alpha and beta chains of ATP synthase. Generally ATPases use the energy from a proton gradient, using the flux of ions across the membrane via the ATPase proton channel, to drive ATP; however, some work in reverse using the energy from the hydrolysis of ATP to create a proton gradient. There are 5 different types of ATPases, which can differ in function, structure and type of ions they transport. The alpha and beta (or A and B) subunits are found in 3 of the different ATPases (F, -V-, and A-). The alpha/A and beta/B subunits are comprised of 3 domains, each centred on the ATP-binding pocket (PFAM:PF00306).