Fig. 3.

Robustness of bistability in monofunctional TCS. Each panel is a two-dimensional section of the parameter space in which bistability is manifested. In each case, the x-axis represents values for the autophosphorylation rate k_ph and the y-axis represents values for one of the other parameters in the model; each physically realizable region of bistability is shaded in grey for each two-dimensional section of parameter space. In each panel, the parameters not explicitly represented are held constant at their values used in Fig. 2 (and summarized in Table 1). The definitions of the parameters are given in Table 1 and in the Modeling procedures section: K_de – dissociation constant of the SK.RR dead-end complex, k_pt – Michaelis–Menten constant of the phosphotransfer reaction, k_pt – rate constant for the molecular activity of the phosphotransfer reaction, K₂ – dissociation constant of the SK–RR∼P complex, k_b2 – rate constant for the binding of SK to RR∼P, K_m – Michaelis–Menten constant of the phosphatase reaction, V_max – maximal velocity of the phosphatase reaction, [SK]_total – total concentrations of SK, and [RR]_total – total concentrations of RR.