Figure 1

(a),(b) Quantitative consistency between predictions and direct simulation results at $\mathrm{SOS}=50$ (intermediate). The fold change in the transition rate (i.e., a larger rate divided by a smaller one) (a) when each rate constant is increased by $1\%$ and (b) when one molecule of each type is added to the system. Each red dot represents the perturbation of (a) a different rate constant and (b) a different species concentration. The direct simulation results are the averages of ten independent FFS runs, and, for each FFS run, ${10}^3$ points were stored on each surface. Only the results for the key reactions, namely, RasGAP catalytic activity, GTP-SOS catalytic activity, and RasGRP catalytic activity, are labeled in (a), and only the results for the key species, namely, RasGAP, SOS, and RasGRP, are labeled in (b). Similar calculations are done at $\mathrm{SOS}=15$ (low) and reported in Fig. S3 [20]. (c) Reaction action is a dominant but not sole factor for sensitivity. Each dot represents the sensitivity and action of one reaction at $\mathrm{SOS}=50$. The rankings of reactions by action and by sensitivity are similar. However, note that the binding (unbinding) reaction of GTP to (from) SOS-GDP, indicated by the blue dot, has small action but large sensitivity. Only the reactions with relatively large sensitivities are labeled.Reuse & Permissions