Intermediate states of actomyosin adenosine triphosphatase

Abstract

The early kinetic steps of actomyosin subfragment 1 (acto-S1) ATPase was investigated by simultaneous monitoring of fluorescence and light scattering and also by observation of the time course of the production of phosphate. Fluorescence enhancement occurred after the dissociation of actomyosin and the rate of enhancement was similar to the maximum rate of enhancement for Sl alone, under similar conditions of pH and temperature. The maximum rate of the phosphate burst for acto-S1 was also approximately the same as that for S1 alone. The maximum rates for fluorescence enhancement or phosphate formation were reached at much lower ATP concentrations for acto-S1 than for S1. An extension of the actomyosin scheme is presented which accounts for these results.