FIGURE 3.

Identification of GLP-1-interacting residues in the second half of GLP1R ECL3. A, the potency of GLP-1 toward chimeric GLP1R, which has the second half of VPAC1R ECL3 (G/V_[E3b]), or mutant G/V_[E3b], into which residues from GLP1R ECL3 were introduced. B, schematic diagram for ECL3 mutations and log EC₅₀ values of GLP-1. The diagram shows that amino acid residues Leu³⁷⁹, Arg³⁸⁰, Phe³⁸¹, and/or Leu³⁸⁴ were reintroduced into G/V_[E3b]. The data on the sigmoidal curves and EC₅₀ values represent the means ± S.E. of at least three independent experiments. ^a, versus wild-type GLP1R (p < 0.05); ^b, versus G/V_[E3b] (p < 0.05).