Fig. 6

Variations in the molecular properties of modulator proteins alter key features of response behavior. The concentration of each modulator protein is set to the level that optimizes the output dynamic range. a Output dynamic range: A_opt as a function of the cooperativity α and the inverse of the relative regulator dissociation constant K_R1. b Graded and switch-like responses: The Hill coefficient computed from the normalized response curves differentiates between modulator proteins which produce graded and switch-like responses. c EC₅₀ and d fractional receptor occupancy at the EC₅₀, plotted as a function of the cooperativity α and the ratio of the ligand affinities, β. In panels b and c we assumed K₁ = [R_T] = 1 μM