Fig. 5.

7TM and ECL mutations alter AC265347 efficacy at the CaSR. (A) Previously published concentration-response curves to Ca²⁺_o in the absence and presence of AC265347 determined in Ca²⁺_i mobilization assays (Leach et al., 2016) were reanalyzed with an operational model of allosterism that accounted for ambient divalent cations (eq. 1) to determine the change in AC265347 efficacy (Δτ_B) at the mutant CaSRs in comparison with the WT receptor. White bars represent no significant change in τ_B. Colored bars that sit above zero represent an increase in τ_B. A significant 1.6–2.5-fold increase in τ_B is represented by the purple bar and a greater than 2.5-fold increase is represented by blue bars. ND, not determined due to negligible efficacy; NA, no PAM activity. Data are the Δτ_B + S.E.M. calculated from WT and mutant τ_B values and experiment numbers shown in Table 2; * demotes significant difference in comparison with WT (P < 0.05, one-way ANOVA with Dunnett’s multiple comparisons post-test). Efficacy residues are shown on a CaSR 7TM domain homology model (B), along with the predicted AC265347 pose from docking studies. Blue and purple colors correspond to the fold change in efficacy shown in (A), whereas red corresponds to a complete loss in AC265347 efficacy.