Energetic Coupling of α E45, α V46, α V132, and α P272
| Receptors . | β . | α . | Θ . | ΔΔGint . | ΔΔΔGint . |
|---|---|---|---|---|---|
| s−1 | s−1 | β/α | kcal/mol | kcal/mol | |
| V132A-P272A | 71800 ± 1680 | 1440 ± 47 | 50 ± 2.0 | −0.66 ± 0.07 | |
| V132L-P272A | 16700 ± 517 | 1290 ± 18 | 13 ± 0.44 | −0.83 ± 0.07 | |
| V132A-P272L | 186 ± 5.4 | 1010 ± 17 | 0.18 ± 0.006 | −1.85 ± 0.06 | |
| V132L-P272L | 62 ± 3.1 | 3240 ± 78 | 0.019 ± 0.001 | −1.48 ± 0.08 | |
| V132A-P272S | 522 ± 12 | 6980 ± 91 | 0.075 ± 0.002 | 2.09 ± 0.05 | |
| V46A-P272A | 40900 ± 1150 | 2550 ± 50 | 16 ± 0.55 | −2.61 ± 0.07 | |
| V46A-P272L | NA | NA | - | - | |
| V46A-P272S | 64 ± 2.1 | 1780 ± 32 | 0.036 ± 0.001 | −0.094 ± 0.07 | |
| V46A-V132A | 797 ± 14 | 12700 ± 150 | 0.081 ± 0.002 | −1.05 ± 0.07 | |
| V46A-V132L | NA | NA | - | - | |
| E45A-V46A | 78 ± 1.3 | 16800 ± 240 | 0.0046 ± 0.0001 | −0.018 ± 0.057 | |
| E45A-V132A | 14000 ± 109 | 17000 ± 108 | 0.82 ± 0.0082 | −0.44 ± 0.04 | |
| E45A-P272A | 83900 ± 1610 | 2150 ± 66 | 39 ± 1.4 | −1.01 ± 0.06 | |
| E45A-P272S | 11400 ± 182 | 6370 ± 59 | 1.79 ± 0.03 | −0.26 ± 0.05 | |
| V46A-P272A-V132A | 7210 ± 77 | 6420 ± 48 | 1.12 ± 0.015 | 2.28 ± 0.05 | |
| V46A-P272S-V132A | 80 ± 2.7 | 13000 ± 380 | 0.0062 ± 0.0003 | −1.00 ± 0.07 | |
| E45A-P272A-V132A | 45300 ± 346 | 6330 ± 61 | 7.2 ± 0.089 | 1.10 ± 0.04 | |
| E45A-P272S-V132A | 2870 ± 486 | 29900 ± 646 | 0.096 ± 0.016 | −0.93 ± 0.18 |
| Receptors . | β . | α . | Θ . | ΔΔGint . | ΔΔΔGint . |
|---|---|---|---|---|---|
| s−1 | s−1 | β/α | kcal/mol | kcal/mol | |
| V132A-P272A | 71800 ± 1680 | 1440 ± 47 | 50 ± 2.0 | −0.66 ± 0.07 | |
| V132L-P272A | 16700 ± 517 | 1290 ± 18 | 13 ± 0.44 | −0.83 ± 0.07 | |
| V132A-P272L | 186 ± 5.4 | 1010 ± 17 | 0.18 ± 0.006 | −1.85 ± 0.06 | |
| V132L-P272L | 62 ± 3.1 | 3240 ± 78 | 0.019 ± 0.001 | −1.48 ± 0.08 | |
| V132A-P272S | 522 ± 12 | 6980 ± 91 | 0.075 ± 0.002 | 2.09 ± 0.05 | |
| V46A-P272A | 40900 ± 1150 | 2550 ± 50 | 16 ± 0.55 | −2.61 ± 0.07 | |
| V46A-P272L | NA | NA | - | - | |
| V46A-P272S | 64 ± 2.1 | 1780 ± 32 | 0.036 ± 0.001 | −0.094 ± 0.07 | |
| V46A-V132A | 797 ± 14 | 12700 ± 150 | 0.081 ± 0.002 | −1.05 ± 0.07 | |
| V46A-V132L | NA | NA | - | - | |
| E45A-V46A | 78 ± 1.3 | 16800 ± 240 | 0.0046 ± 0.0001 | −0.018 ± 0.057 | |
| E45A-V132A | 14000 ± 109 | 17000 ± 108 | 0.82 ± 0.0082 | −0.44 ± 0.04 | |
| E45A-P272A | 83900 ± 1610 | 2150 ± 66 | 39 ± 1.4 | −1.01 ± 0.06 | |
| E45A-P272S | 11400 ± 182 | 6370 ± 59 | 1.79 ± 0.03 | −0.26 ± 0.05 | |
| V46A-P272A-V132A | 7210 ± 77 | 6420 ± 48 | 1.12 ± 0.015 | 2.28 ± 0.05 | |
| V46A-P272S-V132A | 80 ± 2.7 | 13000 ± 380 | 0.0062 ± 0.0003 | −1.00 ± 0.07 | |
| E45A-P272A-V132A | 45300 ± 346 | 6330 ± 61 | 7.2 ± 0.089 | 1.10 ± 0.04 | |
| E45A-P272S-V132A | 2870 ± 486 | 29900 ± 646 | 0.096 ± 0.016 | −0.93 ± 0.18 |
Kinetic parameters and error estimates are derived from global fitting of kinetic scheme to data obtained over a wide range of ACh concentrations (Materials and methods). Gating equilibrium constant (Θ) is ratio of channel opening (β) to closing rate (α) constants. NA, channel openings were detected but clear clusters of openings did not form, preventing kinetic analyses.