Fig. 6.

CaSR PAMs bind with lower affinity in the absence vs. presence of ambient divalent cations, and exhibit differential efficacy at the 7TM domain and ECL mutants. Concentration-response curves to Ca²⁺_o, NPS R568, and AC265347 were determined in Ca²⁺_i mobilization assays in the absence of ambient divalent cations to evaluate PAM efficacy (A–E). Representative mutants were chosen based on their ability to provoke NPS R568 efficacy (G670^ECL2A and A844^7.39V), reduce AC265347 efficacy (A840^7.35V), or have no effect on PAM efficacy (E837^7.32D). Data are mean + S.E.M. pooled from at least four separate experiments performed in duplicate. Curves are the best fit of the data to eq. 2. Vehicle (buffer) is plotted as the smallest [Ca²⁺_o] in accordance with the logarithmic scale.