Figure 5.

Traction force produced by a strong-motor protrusion on rigid substrates reaches a maximum at an intermediate value of the myosin load-free velocity parameter $\omega$. (A) Optimum myosin activity parameter for maximum traction force on rigid substrates as a function of $\omega$ for four different values of the clutch kinetic parameter $\tau$. The optimum activity ${\mathrm{F}}^{\mathrm{o}\mathrm{p}\mathrm{t}}$ monotonically decreases with $\tau$ and $\omega$. (B and C) Dimensionless time-averaged traction force (B) and average fraction of bound clutches (C) for a strong-motor protrusion ($\mathrm{F}\to \infty$) on rigid substrates ($\mathrm{K}\to \infty$), as a function of $\omega$ for five different values of $\tau$. Force transmission shows a biphasic dependence on the parameter $\omega$, with an optimum ${\omega }^{\mathrm{o}\mathrm{p}\mathrm{t}}$ that increases linearly with $\tau$ (see inset in (B)). Number of bound clutches increases monotonically with $\tau$ and $\omega$. Solid lines correspond to the analytical solutions of the mean-field model (Eqs. S55 and S57), and symbols are the solutions of the stochastic model. Near-perfect agreement is found between analytical and stochastic solutions. To see this figure in color, go online.