Functional selectivity of agonists in the quartic ternary complex model.

(A, B) We simulated the GPCR-mediated (in)activation two target G proteins by several ligands. A dose-response for each ligand and G protein pair shows the amount of receptor species capable of signalling (R_saG+R_taG+LR_saG+LR_taG) as a fraction of the total number of receptors and against the concentration of ligand (arbitrary units). The concentrations of receptor and G protein are unity. Parameter values: KactL = 1, KactG = 0.05, Γ = 1, affinities for L1 are given by: (Ka′, α_t, α_a, α_at) = (10,0.1,10,1), for L2: (1,20,20,400), L3: (0.1,10,10,0.01), L4: (100,0.1,0.4,0.01) L5: (20,20,0.05,5), G1: (Kg′, β_t, β_a, β_at) = (10,0.1,10,1) and G2: (1,10,10,100).