Fig. 5.

β-arrestin recruitment activity of (A) DRD2, (B) GRPR, (C) HCRTR2, and (D) MTNR1A mutants. (i) Representative Tango assay dose–response curves. Points indicate means ± SEM of technical replicates. EC₅₀ (ii) and efficacy (iii) were determined from dose–response curve fits, and surface expression (iv) was measured by cell ELISA (DRD2, HCRTR2) or immunofluorescence microscopy (GRPR, MTNR1A), as described in Materials and Methods. Points represent means from independent experiments, and error bars show SEM. Mutants were compared to WT using one-way ANOVA and Dunnett’s posttest, except where only one mutant was analyzed, in which case a t test was used (*P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001). For mutants which did not reach a plateau in the dose–response curves, EC₅₀ and efficacy determinations are estimates and represent lower limits.