TABLE 1.

Comparison of β₂AR-WT and β₂AR-F193A

pEC50 ± SD						Maximum
Assay	WT	F193A	Shift	Significant		WT (%)	F193A (%WT)	Significant	SI (%)
Arrestin BRET	7.71 ± 0.29	5.26 ± 0.11	2.45	Y		100	56.4 ± 4.7	Y	60.8
cAMP	7.92 ± 0.47	7.86 ± 0.41	0.06	N		100	111.9 ± 4.1	N	98.4
mGs BRET	7.98 ± 0.55	6.67 ± 0.26	1.31	Y		100	102.2 ± 9.6	N	99.9

Comparison of Wild-type β₂-adrenergic receptor (β₂AR-WT) and β₂AR-F193A across assays. Negative log of the half-maximal effective concentration (pEC₅₀) values and maximum response relative to β₂AR-WT are listed. Shift indicates the difference in pEC₅₀ values for β₂AR-WT and β₂AR-F193A. Significance for pEC₅₀ and maximum response was determined by t test for n = 3 experiments. Stimulus inactivation indicates a comparison of agonist doses that promote equal response in WT and mutant receptor in each assay. This parameter was estimated as described previously (Ostrom and Ehlert, 1997). Briefly, equiactive isoproterenol concentrations were compared between β₂AR-WT and β₂AR-F193A by interpolating equivalent β₂AR-F193A responses from β₂AR-WT dose response curves. The stimulus inactivation (SI) parameter denotes the apparent efficacy of β₂AR-F193A compared with wild-type.