Figure 3.

Stochastic simulation data (data points) and analytical master equation results (solid lines) for the mean MT length 〈x_MT〉 as a function of stathmin/tubulin s = S_tot/[T₀]. We compare the system with constitutively active Rac (r_on = 1, solid lines and crosses) to the system without Rac (r_on = 0, shaded lines and circles) both for tubulin-sequestering stathmin (A) and catastrophe-promoting stathmin (B). (Hatched area) Possible MT length gain by Rac regulation. (Shaded area) Region in which MTs exhibit bimodal length distributions for constitutively active Rac. (Insets a–c) Corresponding MT length distributions for three particular values of s with (a) s < s_λ, (b) s = s_λ, and (c) s > s_λ.