The Rate of Release of ATP from Its Complex with Myosin

Abstract
An approach for measurement of the rate of dissociation of ATP from its complex with myosin was carefully evaluated. The procedure was found valid, and the off constant (21.degree. C, I [ionic strength] = 0.21 M, pH 7.0) is 1 .times. 10-4 s-1. Other data for the rate of ATP binding give a Kd for myosin ATP of 6 .times. 10-11 M. Reasons for the apparent discrepancy between this value and that reported by others were examined. When various factors are appropriately taken into account, this discrepancy is eliminated.