Figure 2.

Myosin filament processivity depends on motor properties and external force. (A) Simulated F-actin trajectories for different values of N_heads. The actin filament was assumed to return to its original position upon release by the myosin. Each curve represents a single simulation. (B) The mean attached time as a function of N_heads showed a shift under stalled compared with unloaded conditions. (C) Mean attached time on an unloaded F-actin for a range of N_heads and ρ_d(0). The boxes indicate published values for muscle myosins, nonmuscle myosin IIB, and nonmuscle myosin IIA (see main text for references) starting at the top left and going clockwise. (D) Increased mean attached time for a stalled F-actin over the same range as in (C). Parameter values: (A) ρ_d(0) = 0.34 (k_on = 10s⁻¹, k_off(0) = 19.1 s⁻¹), F_ext = 4 pN; (B) ρ_d(0) = 0.05 (k_on = 10 s⁻¹ and k_off(0) = 191 s⁻¹); (C and D) k_on = 10 s⁻¹. Averages in (B)–(D) were taken over 1000 s of simulation time. The standard error in B was smaller than the data points. The distribution of t_attach is described in Fig. S9. To see this figure in color, go online.