TABLE 2.
Summary of signaling properties (EC50 values) of highly conserved and T2R1-specific transmembrane mutant receptors obtained from cell-based calcium assay
The values are expressed as the mean ± S.E. (n = 2–5 experiments) in duplicate, using the agonist dextromethorphan.
| Receptor | Transmembrane helix | EC50 | EC50 mutant/EC50 WT |
|---|---|---|---|
| μm | |||
| Wild type | 97 ± 21 | 1.0 | |
| N24A | I | No responsea | |
| N24D | I | No response | |
| I27A | I | 153 ± 17 | 1.59 |
| I27V | I | 140 ± 11 | 1.45 |
| L51A | II | 133 ± 20 | 1.38 |
| L51V | II | 180 ± 6 | 1.85 |
| R55A | II | 155 ± 13 | 1.59 |
| R55K | II | 168 ± 50 | 1.73 |
| N66A | II | No response | |
| N66D | II | No response | |
| E74A | II | 154 ± 20 | 1.58 |
| E74Q | II | 166 ± 7 | 1.71 |
| N89A | III | No response | |
| N89D | III | No response | |
| W94F | III | 118 ± 40 | 1.21 |
| W94Y | III | 249 ± 33 | 2.56 |
| L99A | III | 168 ± 9 | 1.73 |
| L99V | III | 211 ± 45 | 2.17 |
| L197A | V | 135.3 ± 9 | 1.39 |
| L197V | V | No response | |
| S200A | V | 147 ± 10 | 1.51 |
| S200T | V | No response | |
| L201A | V | 104.2 ± 40 | 1.07 |
| L201V | V | No response | |
| H273S | VII | No response | |
| H273F | VII | 164 ± 18 | 1.69 |
| L277A | VII | 158.9 ± 33 | 1.62 |
| L277V | VII | 168 ± 21 | 1.73 |
| I278A | VII | 174.1 ± 30 | 1.79 |
| I278V | VII | 226 ± 8 | 2.32 |
a No response, those mutants where there is no agonist concentration-dependent response, or the observed specific response is below the base-line activity of wild type T2R1.