Figure 8.

Kinetics of P_i release from 1IQ as a function of actin concentration. Myosin V 1IQ (4.0 μM) was mixed with 1 mM MgATP, aged for 14 ms to populate the weak-binding states then mixed with a solution of actin filaments and P_i-binding protein. Time courses fit two exponentials. The fast rate (●) corresponds to a phosphate burst during the first turnover of ATP with a stoichiometry of one P_i/myosin and the slow rate (○) to yields the steady-state ATPase rate at 1 μM ADP. Final concentrations at t = 0 were 1.0 μM 1IQ, 250 μM MgATP, 10 μM P_i-binding protein, and the indicated actin filament concentrations.