ATP synthase turns a flow of protons into ATP. Protons cross the membrane through the Fo motor and spin a ring of c subunits. The ring turns a central stalk inside the F1 head. Each 120° turn of the stalk changes the shape of the three catalytic β subunits and releases one ATP.
- Where
- Inner membrane of mitochondria, thylakoid membrane of chloroplasts, and the plasma membrane of bacteria.
- Power
- Proton-motive force across the membrane (sodium-motive force in some bacteria). With ATP and no gradient, the same machine runs backward and pumps ions.
~100 turns/s
Turn rate in mitochondria
98–15 c subunits
c-ring size across species
9