Mechanical rotation of the c subunit oligomer in ATP synthase (F0F1): Direct observation

Abstract

F0F1, found in mitochondria or bacterial membranes, synthesizes adenosine 5'-triphosphate (ATP) coupling with an electrochemical proton gradient and also reversibly hydrolyzes ATP to form the gradient. An actin filament connected to a c subunit oligomer of F0 was able to rotate by using the energy of ATP hydrolysis. The rotary torque produced by the c subunit oligomer reached about 40 piconewton-nanometers, which is similar to that generated by the γ subunit in the F1 motor. These results suggest that the γ and c subunits rotate together during ATP hydrolysis and synthesis. Thus, coupled rotation may be essential for energy coupling between proton transport through F0 and ATP hydrolysis or synthesis in F1.