Single-Molecule Studies of Rotary Molecular Motors

Abstract

Rotary molecular motors are protein complexes that transform chemical or electrochemical energy into mechanical work. There are five known rotary molecular motors in nature; the bacterial flagellar motor, and two motors in each of ATP-synthase and V-ATPase. Rotation of the flagellar motor drives a helical propeller that powers bacterial swimming. The function of the other rotary motors is to couple electrochemical ion gradients to synthesis or hydrolysis of ATP, and rotation is a detail of the coupling mechanism rather than the ultimate purpose of the motors. Much has been learned about the mechanism of the F1 part of ATP-synthase and the flagellar motor by measuring the rotation of single motors with a variety of techniques under a wide range of conditions. This chapter will review the structures of ATP-synthase and the flagellar motor, and what has been learned about their mechanisms using single molecule techniques.