Effects of replacement of amino acids in TM2 of the β1AR with alanine on ligand-binding characteristics of the β1AR
| 125I-CYP | Ligands (Ki) | ||||
|---|---|---|---|---|---|
| Kd | Bmax | T-0509 | Denopamine | Xamoterol | |
| pM | pmol/mg | nM | |||
| WT β1AR | 50.7 ± 5.7 | 28.1 ± 3.0 | 200 ± 10 | 1200 ± 40 | 110 ± 18 |
| M98A- | 42.8 ± 2.1 | 12.5 ± 1.0 | 120 ± 6 | 1100 ± 110 | 80 ± 12 |
| S102A- | 67.3 ± 11.8 | 63.6 ± 10.6 | 220 ± 16 | 1500 ± 250 | 120 ± 5 |
| L110A- | 38.2 ± 6.1 | 16.5 ± 2.2 | 760 ± 110b | 4700 ± 310b | 220 ± 40 |
| T117A- | 47.1 ± 7.4 | 6.1 ± 0.2 | 620 ± 38b | 6700 ± 600b | 280 ± 110 |
| I118A- | 55.5 ± 7.3 | 19.8 ± 2.9 | 190 ± 14 | 1900 ± 450 | 130 ± 36 |
| V119A- | 46.9 ± 8.5 | 17.0 ± 3.1 | 210 ± 20 | 1600 ± 310 | 360 ± 91 |
| V120A- | 59.0 ± 13.3 | 16.6 ± 3.2 | 420 ± 786-a | 3300 ± 8606-a | 230 ± 60 |
| W121A- | 46.1 ± 10.1 | 22.3 ± 4.6 | 190 ± 37 | 1200 ± 190 | 90 ± 3 |
The binding of ligands to the WT β1AR and alanine-substituted β1AR mutants were determined by competition with 50 pM125I-CYP. The data were analyzed using the nonlinear least-squares regression computer program as described underExperimental Procedures. The results are shown as the mean ±S.E. from three to four separate experiments.
↵6-a P < 0.05,b P < 0.01 compared with the WT β1AR.