Operation of the F(0) motor of the ATP synthase.

ATP, the universal carrier of cell energy is manufactured from ADP and phosphate by the enzyme ATP synthase using the energy stored in a transmembrane ion gradient. The two components of the ion gradient (DeltapH or DeltapNa(+)) and the electrical potential difference Deltapsi are thermodynamically but not kinetically equivalent. In contrast to accepted wisdom, the electrical component is kinetically indispensable not only for bacterial ATP synthases but also for that from chloroplasts. Recent biochemical studies with the Na(+)-translocating ATP synthase of Propionigenium modestum have given a good idea of the ion translocation pathway in the F(0) motor. Taken together with biophysical data, the operating principles of the motor have been delineated.