Figure 4

Simulations from four sub-models of the ternary-complex model, TCM. For sub-model definitions see Table 2. Parameters A _s and A _m, equilibrium association constants for ligands S and M, are kept at unity. Parameter c, the cooperativity constant for binding, is varied by a factor 10³ in three steps for each sub-model as indicated in the panels. Red curves indicate orthoster concentration-response curves in the absence of an alloster. In all panels the alloster M concentration is varied in four steps: in panels A-I by a factor 10² from 1x10^-2 to 1x10⁴; in panels G-K by a factor 10 from 1x10^-2 to 1x10¹ and in panel L by a factor 10² from 1x10^-3 to 1x10³. Green curves with circles show the actual EC₅₀ and the black circle represents the position of a limiting EC₅₀ for M → ∞.