The Rate of Release of ATP from Its Complex with Myosin

An approach previously published from this laboratory for measurement of the rate of dissociation of ATP from its complex with myosin has been carefully evaluated. The procedure has been found valid, and the off constant (21 degrees C, 1=0.21 M, pH 7.0) is 1x 10(-4)s(-1). Other data for the rate of ATP binding give a Kd for myosin ATP of 6x10(-11) M. Reasons for the apparent discrepancy between this value and that reported by others have been examined. When various factors are appropriately taken into account, this discrepancy is eliminated.