[35S]GTPγS binding to reconstituted vesicles containing M2 receptors and Go proteins at different concentration ratios, with the concentration of Go held constant
| R/Go ratio expected | |||||
|---|---|---|---|---|---|
| 1:100 | 10:100 | 50:100 | 10:0 | 0:100 | |
| B max for [3H]QNB (fmol/tube) | 4.20 ± 0.04 | 38.2 ± 0.3 | 199 ± 3 | 38.5 ± 0.3 | |
| Overall concentration of [3H]QNB binding sites (pm) | 21 | 191 | 995 | 192 | 0 |
| B max for [35S]GTPγS (fmol/tube) | 444 ± 3 | 441 ± 8 | 436 ± 4 | 452 ± 6 | |
| Overall concentration of [35S]GTPγS binding sites (pm) | 2220 | 2205 | 2180 | 0 | 2260 |
| R/Go obtained | 0.0097 ± 0.0001 | 0.089 ± 0.001 | 0.454 ± 0.008 | ||
| k obs(min−1) without muscarinic ligand | 0.029 ± 0.001 | 0.044 ± 0.000 | 0.128 ± 0.001 | 0.026 ± 0.000 | |
| k obs (min−1) in the presence of | |||||
| 1 mm carbachol | 0.173 ± 0.002 | 0.179 ± 0.001 | 0.195 ± 0.003 | 0.027 ± 0.000 | |
| 10 μm alcuronium | 0.040 ± 0.000 | 0.043 ± 0.001 | 0.045 ± 0.001 | 0.026 ± 0.000 | |
| 100 nm atropine | 0.028 ± 0.000 | 0.029 ± 0.000 | 0.031 ± 0.000 | 0.027 ± 0.000 | |
| Emax (fold over basal) for | |||||
| Carbachol | 3.27 ± 0.04 | 2.32 ± 0.00 | 1.30 ± 0.00 | ||
| Alcuronium | 1.28 ± 0.01 | 0.50 ± 0.01 | |||
| Atropine | 0.81 ± 0.01 | 0.37 ± 0.00 | |||
| EC50 (μm) for | |||||
| Carbachol | 8.06 ± 0.18 | 16.62 ± 0.12 | 25.72 ± 0.23 | ||
| Alcuronium | 1.760 ± 0.014 | 0.651 ± 0.011 | |||
| Atropine | 0.0016 ± 0.0000 | 0.0010 ± 0.0000 | |||
Values were derived from the experiments shown in Figs. 1 and 3. They are mean ± standard error of three experiments performed with incubations in duplicate.