Figure 5.

Mean-field results. (A) Force-velocity relationship in dependence of N_a/N. The black line indicates microtubule gliding under friction. The force-velocity curves for N_a/N < 0.7 lead to negative forces (i.e., toward the negative x direction in Fig. 1A), as inactive motors dominate, resulting in stopping of the microtubule. For N_a/N = 0.7, both positive and negative forces are possible and two stable solutions exist. For N_a/N > 0.7, microtubules are under positive forces, leading to gliding with positive velocities. (B) Phase diagram parameterized with N_a/N and the detachment rate of the inactive motor in the absence of forces ${\omega }_{\text{p}}^0$ for the mean-field approach (blue circles) and the simulation (red circles). Symbols represent the lower and upper critical ratios, which confine the region of coexistence of fast and slow motilities. We note that even for motor numbers as small as N = 20 (red circles), the simulation results agree well with the mean-field approach. The parameter values are the same as those used for the simulation results in Fig. 2B.