Table 3

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

ConstructISOSALDOBEPHDCI
β2AR-GsαL 1.7  ± 0.539  ± 2390  ± 16923  ± 27013  ± 12
β2AR-GsαS 6.2  ± 3.3167  ± 78310  ± 1083600  ± 49836  ± 15
β2AR-Giα2 31  ± 16712  ± 4011860  ± 8901850  ± 50015  ± 8
β2AR-Giα3 42  ± 18809  ± 241155  ± 90917  ± 103-a
β2AR-G16α 143  ± 69587  ± 311595  ± 1095990  ± 2130
β2AR-G 23  ± 13310  ± 132540  ± 2114670  ± 1110

For determination of the potencies 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 EC50 values are given in nM and were calculated by nonlinear regression. Data shown are the means ± S.D. values of three independent experiments performed in triplicates.

    • 3-a  —, DCI-stimulated GTPγS binding was too small to calculate an EC50 value.