Effects of mutations in o3/TM7 region on allosteric interactions
Affinities (expressed as pKapp) for gallamine and W84 are shown, along with half-times of dissociation of [3H]NMS in the absence of allosteric modulators. To facilitate comparisons, the affinit y data have also been transformed to a scale of relative difference between the p Kapp values of the human M2 and M5 receptors (see Materials and Methods). Data shown represent mean ± S.E.M. from three or more assays for pKapp values and six or more assays for half-times. Receptors were expressed in COS-7 cell membranes.
| Receptors | t1/2 | pKapp Values | Relative pKapp | ||
|---|---|---|---|---|---|
| Gallamine | W84 | Gallamine | W84 | ||
| min | mean ± S.E.M. | % | |||
| M2 | 4.3 ± 0.4 | 6.99 ± 0.06 | 7.66 ± 0.10 | 100 | 100 |
| M5 | 95.2 ± 0.6 | 5.02 ± 0.04 | 5.66 ± 0.07 | 0 | 0 |
| M2 N419K | 7.4 ± 0.3 | 5.89 ± 0.09 | 6.76 ± 0.10 | 44.2 | 55.0 |
| M2 N419V | 3.7 ± 0.1 | 7.20 ± 0.04 | 8.11 ± 0.11 | 110.7 | 122.5 |
| M2 T423H | 14.1 ± 0.9 | 6.38 ± 0.03 | 6.76 ± 0.11 | 69.0 | 55.0 |
| M5 V474N | 85.5 ± 4.7 | 5.55 ± 0.03 | 5.29 ± 0.09 | 26.9 | −18.5 |
| M5 H478T | 37.6 ± 1.6 | 5.83 ± 0.10 | 6.27 ± 0.11 | 41.1 | 30.5 |
| M5 V474N, H478T | 26.7 ± 0.6 | 5.65 ± 0.08 | 6.13 ± 0.09 | 32.0 | 23.5 |