Effects of mutations on the functional responses. A, effects of mutational changes in receptor binding affinity (pIC50 values) on the functional potency (pEC50 values). Inset, mutants of Phe178(4.64) only: GnRH I, ●; GnRH II, △. B, effects of mutations on the maximum signaling efficacy. *, denotes mutants pretreated with NBI-42902. For detailed results see Tables 1 and 3.