Figure 3. Growth of filaments from two inequivalent nucleating centers in a limiting pool of monomers.

(A) Schematic showing the growth of filaments (pink) from two distinct nucleating centers (green) in a pool of monomers (in red). (B) (Inset) Numerical simulation of the growth trajectory of the filaments from the nucleating centers. Shown are trajectories for 10% difference in assembly rate (dark) and 1% difference (light). After a growth phase, where both filaments accrue monomers, the faster growing filaments attains a steady state by taking up most of the free monomers, while the slower filament shrinks. The faster growing filament attains a peaked distribution of size (black) and the slower one attains a geometric distribution (red). The parameters used are ${k_{1,+}^{\prime }}^{10\%}=0.55N_{\mathit{free}}^{-1}{s}^{-1}$, ${k_{1,+}^{\prime }}^{1\%}=0.505N_{\mathit{free}}^{-1}{s}^{-1}$, ${k_{2,+}^{\prime }}^{1\%}=0.5N_{\mathit{free}}^{-1}{s}^{-1}$, k₋ = 10 s⁻¹, N = 1000 and N_free = N − l₁ − l₂, is the number of free monomers in solution and l₁ and l₂ are the lengths of the two filaments. The simulations are overlaid on the results obtained analytically (blue and green) in STAR Methods, section “Gamma function representation of two filaments”.