Mechanism of actomyosin ATPase and the problem of muscle contraction.

Publisher Summary This chapter discusses the mechanism of actomyosin ATPase and the problem of muscle contraction. Actomyosin, like any other enzyme, brings about the hydrolysis of its substrate by a series of intermediate steps. The purpose of kinetic studies is to determine the sequence of intermediate steps in the mechanism and to measure the respective rate constants. The well known sliding filament model of Hanson and Huxley attributes the shortening of a sarcomere to the relative motion of the thin filaments with respect to the thick filaments. Experiments have failed to detect any change in thick and thin filament lengths with sarcomere length. The force that produces sliding or the development of tension at fixed length must be attributed either to the direct action, and consequently the movement of the cross bridges, or to electrostatic and van der Waals forces possibly mediated by the cross bridge projections but not requiring to and fro movements of the bridges