Table 1.

Summary of ligand binding properties of wild-type β₂-AR and mutant receptors

Receptor	Transmembrane helix	Kd, nM	95% confidence intervals	Bmax, pmol/mg
Wild type		2.1	1.70–2.40	18 ± 2.2
A76S	II	1.2	0.92–1.39	12 ± 0.5
A76L	II	1.4	1.10–1.67	14 ± 0.4
A76V	II	1.4	1.00–1.28	9.1 ± 0.2
A78S	II	1.5	1.14–1.73	17 ± 1.1
A78L	II	0.9	0.47–1.39	9.0 ± 0.6
A78V	II	1.4	1.14–1.73	19 ± 0.4
S120A	III	2.3	1.77–2.96	28 ± 1.2
S120L	III	1.5	0.81–2.14	4.3 ± 0.3
S120V	III	1.6	0.58–2.62	4.9 ± 0.5
A128S	III	2.2	1.58–2.92	28 ± 1.4
A128L	III	3.2	1.00–5.39	4.8 ± 0.5
A128V	III	1.6	1.31–1.83	16 ± 0.5
S161A	IV	2.7	1.98–3.55	33 ± 2.0
S161L	IV	ND		ND
S161V*	IV	2.0	0.80–3.14	2.7 ± 0.4
S165A	IV	4.7	3.54–5.98	15 ± 0.8
S165L	IV	ND		ND
S165V	IV	1.2	0.68–1.71	6.7 ± 0.4

The values are expressed as the mean ± SE (n = 3–5 experiments). ND, not detected (no significant specific binding detected under the assay conditions).

*High nonspecific binding (15–20% of total binding).