Figure 1 : Rotary catalysis and proton pumping by V-ATPase.

From: Oscillating Electric Field Measures the Rotation Rate in a Native Rotary Enzyme

Figure 1

ATP binding and hydrolysis drives the rotor and rotation drives proton transport. Each subunit c (the composition of the so-called c-ring is actually c4c′c″) carries a proton, when in contact with lipids. Protons enter and leave the rotor in hydrophilic input and output hemichannels between the c-ring and subunit a, respectively.