Appendix 1—figure 2. Predictions for the elongation velocity $v_{\text{elong}}$ (a) and the formin dissociation rate $k_{\text{off}}$ (b) as functions of the profilin concentration within the approximation of strong actin-profilin binding of Eq.(A13).

While the exact position of the curves is dependent on the choice of parameters as indicated on the figure, their qualitative shapes are a robust prediction of the model, and agree well with the experimental data presented in Figure 3B of main text.