Effects of replacement of transmembrane regions with corresponding portions of the β1AR on ligand-binding characteristics of the β2AR
| 125I-CYP | Ligands (Ki) | ||||||
|---|---|---|---|---|---|---|---|
| Kd | Bmax | Propranolol | Salbutamol | Formoterol | Procaterol | IPS-339 | |
| pM | pmol/mg | nM | |||||
| β2AR | 23.2 ± 3.1 | 4.4 ± 0.4 | 1.1 ± 0.3 | 1500 ± 170 | 27 ± 10 | 70 ± 20 | 0.4 ± 0.1 |
| CH-1 | 56.1 ± 0.6 | 4.4 ± 0.1 | 2.2 ± 0.3 | 4100 ± 440 | 74 ± 9 | 280 ± 74 | 2.0 ± 0.7 |
| CH-2 | 15.8 ± 0.8 | 4.9 ± 0.01 | 1.8 ± 0.4 | 10,000 ± 330c | 190 ± 15 | 1200 ± 1301-a | 1.4 ± 0.2 |
| CH-3 | 47.3 ± 3.6 | 23.6 ± 1.4 | 2.3 ± 0.2 | 2000 ± 410 | 38 ± 5 | 400 ± 25 | 3.3 ± 0.6 |
| CH-4 | 142 ± 14c | 54.5 ± 5.9 | 2.2 ± 0.2 | 3000 ± 190 | 270 ± 27 | 1800 ± 140b | 2.9 ± 0.2 |
| CH-5 | 54.1 ± 3.2 | 28.3 ± 0.3 | 4.8 ± 0.3c e | 7700 ± 770b e | 1900 ± 100c | 6800 ± 560c | 20 ± 1c |
| CH-6 | 66.7 ± 11.01-a | 6.6 ± 0.3 | 9.6 ± 1.1c | 8600 ± 940c d | 920 ± 200c e | 3300 ± 270c e | 21 ± 2c |
| CH-7 | 129 ± 24c e | 2.2 ± 0.7 | 2.8 ± 0.4e | 11,000 ± 2800c | 450 ± 1101-a e | 3600 ± 590c e | 5.3 ± 1.51-a e |
| CH-8 | 40.6 ± 2.2 | 0.2 ± 0.1 | 0.9 ± 0.2e | 1500 ± 600e | 47 ± 8e | 110 ± 11e | 0.8 ± 0.2e |
| β1AR | 36.9 ± 5.2 | 19.9 ± 5.6 | 9.7 ± 1.2 | 17,000 ± 2400 | 2400 ± 260 | 8000 ± 870 | 18 ± 3 |
The binding of ligands to the WT-β2AR and β1/β2-chimeric receptors were determined by competition with 50pM 125I-CYP. The data were analyzed using the nonlinear least-squares regression computer program as described under Experimental Procedures. The results are shown as the mean ± S.E. from three to four separate experiments.
↵1-a P < 0.05;b P < 0.01; c P < 0.001 compared with the WT β2AR; d P< 0.01, e P < 0.001 compared with the WT β1AR.