Effects of replacement of transmembrane regions with corresponding portions of the β2AR on ligand-binding characteristics of the β1AR
| 125I-CYP | Ligands (Ki) | |||||||
|---|---|---|---|---|---|---|---|---|
| Kd | Bmax | T-0509 | T-1583 | Xamoterol | Prenalterol | Denopamine | Dobutamine | |
| pM | pmol/mg | nM | ||||||
| β2AR | 16.4 ± 0.7 | 3.4 ± 0.1 | 1700 ± 42 | 4100 ± 180 | 1400 ± 210 | 410 ± 21 | 5000 ± 100 | 1400 ± 87 |
| CH-1 | 18.6 ± 0.2 | 1.7 ± 0.1 | 1300 ± 472-a | 1200 ± 41 | 4600 ± 660 | |||
| CH-2 | 24.0 ± 0.72-a | 3.8 ± 0.5 | 240 ± 11c | 100 ± 5c | 410 ± 47b | |||
| CH-3 | 43.4 ± 1.7c | 19.4 ± 1.6 | 980 ± 130 | 1300 ± 120 | 11,000 ± 860c | |||
| CH-4 | 47.9 ± 2.1c | 8.4 ± 0.6 | 120 ± 9 | 73 ± 3c | 810 ± 532-a | |||
| CH-5 | 35.3 ± 2.4c | 28.9 ± 3.9 | 120 ± 10c | 100 ± 5c | 1400 ± 792-a | |||
| CH-6 | 29.6 ± 1.4c | 2.8 ± 0.2 | 2300 ± 190b f | 1200 ± 99f | 14,000 ± 2200c f | |||
| CH-7 | 45.9 ± 3.2c f | 0.6 ± 0.1 | 940 ± 110c f | 510 ± 54c e | 3100 ± 510 | |||
| CH-8 | 18.0 ± 0.8f | 0.4 ± 0.01 | 140 ± 5c | 1100 ± 73f | 3400 ± 350 | |||
| β1AR | 32.1 ± 2.4 | 23.9 ± 3.1 | 200 ± 9 | 2100 ± 170 | 100 ± 4 | 280 ± 10 | 1500 ± 88 | 3200 ± 130 |
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.
↵2-a P < 0.05;b P < 0.01; c P < 0.001 compared with the WT-β2AR; d P< 0.05, e P < 0.01,f P < 0.001 compared with the WT-β1AR.