Chemomechanical coupling mechanism of F(1)-ATPase: catalysis and torque generation.

F1-ATPase (F1), a rotary motor protein driven by ATP hydrolysis, is unique with respect to its high efficiency and reversibility in converting chemical energy into mechanical work. Single-molecule studies have improved our understanding about the energy-conversion mechanism of F1 and the chemomechanical-coupling scheme under ATP hydrolysis conditions. A novel single-molecule technique was recently established to estimate the free-energy change of F1 during catalysis at elementary-step resolution, advancing our understanding about the energy-conversion mechanism of ATP hydrolysis and synthesis. The energy conversion mechanism of F1 elucidated from single-molecule studies provides us with important insights into the operating principles underlying molecular motors.