Table 2

Efficacies of β2AR ligands at stimulating GTPγS binding to β2AR-G fusion proteins

ConstructISOSALDOBEPHDCIICI
β2AR-GsαL 1.001.03  ± 0.030.98  ± 0.060.87  ± 0.070.67  ± 0.08−0.15  ± 0.01
β2AR-GsαS 1.000.81  ± 0.040.68  ± 0.020.33  ± 0.100.19  ± 0.04−0.05  ± 0.02
β2AR-Giα2 1.000.64  ± 0.100.40  ± 0.020.35  ± 0.020.29  ± 0.07−0.02  ± 0.01
β2AR-Giα3 1.000.55  ± 0.030.52  ± 0.080.31  ± 0.020.15  ± 0.03−0.05  ± 0.02
β2AR-G16α 1.000.64  ± 0.130.35  ± 0.110.26  ± 0.080.08  ± 0.030.00  ± 0.01
β2AR-G 1.001.00  ± 0.060.48  ± 0.030.48  ± 0.110.08  ± 0.04−0.04  ± 0.04

For determination of the efficacies of ligands, GTPγS binding was measured in Sf9 membranes expressing β2AR-G at 3.7 to 13.0 pmol/mg with 0.4 nM [35S]GTPγS as described under Experimental Procedures. The incubation time was 45 min. Reaction mixtures contained ligands at 0.1 nM to 1 mM as appropriate to obtain saturated concentration-response curves. The concentration-response curves were generated by nonlinear regression analysis, and the plateau values for each ligand were divided by the (maximal) plateau value of ISO to calculate the efficacies. The inhibitory effects of ICI are referred to the stimulatory effects of ISO. Data shown are the means ± S.D. values of three independent experiments performed in triplicates.