Fig. 5.

Trajectories of steady state simulations for the output (Ssk1, dark blue) with $k_1=2{\text{s}}^{-1}$ and two different values of $k_4$. a A combination that activates the downstream pathway constitutively due to a high level of dephosphorylated Ssk1 and is hence not fit for transmitting the signal. b A “feasible parameter combination”, exhibiting only a basal level of dephosphorylated Ssk1 in steady state. This allows for a functional pathway and can be further investigated. a $k_4=0.5{\text{s}}^{-1}$. b $k_4=0.25{\text{s}}^{-1}$. (Color figure online)