Fig. 2.

Gαs-mediated signaling activity of wild-type (WT) and group-conserved mutant β₂-ARs as measured by cAMP accumulation assay. Shown are the basal activity (−) and activity after stimulation (+) with 10 μM isoproterenol. Results are normalized to the basal activity of wild-type receptors. The relative activation rates of β₂-AR mutants present in H2 (A), H3 (C), H4 (B), and the compensatory mutants (D) are shown. Results are from at least three independent experiments performed in duplicate.