Modulation of the sliding movement of myosin-driven actin filaments associated with their distortion: The effect of ATP, ADP, and inorganic phosphate

Abstract

The motility of actin filaments interacting with myosin motors during ATP hydrolysis can be evaluated using an in vitro motility assay. Motility assays with fluorescence imaging techniques allow us to measure the sliding velocity as an index of motility and fluctuations of actin filaments at nanometer accuracy. Because actin filaments are flexible, distortions such as deformation of their filamentous structure are also observed during the sliding movement. This chapter discusses an imaging analysis of velocity fluctuation and distortion of actin filaments in the case of myosin II motors derived from skeletal fast muscle. The relationship between the velocity and distortion is discussed. In addition, the effect of ADP and inorganic phosphate (Pi), which are products of ATP hydrolysis, on this relationship is explained through the kinetics of myosin-actin binding. Considering the fluctuation studies conducted to date, we review our concept with respect to the coordination of motion along single actin filaments, wherein distortions alter the geometric features surrounding actin-myosin in terms of water behavior.