Embedded in the membrane, a ring of 10 to 14 c-subunits rotates during proton transport. The proton entrance and exit channel are probably located in the a-subunit (the non-rotating counterpart together with the b-subunits of F_o).

Proton uptake and release at the a- and c-subunit interface might involve a helix rotation within the c-subunit (‘swivelling mechanism’).