Table 2.
Second-order reaction rate constants for MTSEA applied in the absence or presence of ACh with the Cys mutants
| Construct | τ in the absence of ACh (m−1 s−1) | n | τ in the presence of ACh (m−1 s−1) | n |
|---|---|---|---|---|
| αG275Cβγδ | 27.5 ± 2.4 | 3 | 22.2 ± 3.3 | 3 |
| αI274Cβγδ | nt | 8.7 ± 2.6*** | 3 | |
| αP272Cβγδ | 274 ± 15 | 4 | 426 ± 66* | 3 |
| αV271Cβγδ | 102 ± 10 | 4 | 398 ± 73*** | 3 |
| αS269Cβγδ | 93,800 ± 9100 | 3 | 273,100 ± 31,000** | 3 |
| αT267Cβγδ | 510 ± 54 | 4 | 5,450 ± 86*** | 3 |
| αS266Cβγδ | 12,200 ± 2200 | 4 | 6,970 ± 1800 | 3 |
| αP265Cβγδ | 40,100 ± 3700 | 5 | 3940 ± 620*** | 3 |
| αI264Cβγδ | 16.3 ± 2.1 | 4 | 22.8 ± 6.5 | 4 |
| αL263Cβγδ | 45.0 ± 13.0 | 3 | 39.3 ± 7.4 | 3 |
| 717 ± 105 | 870 ± 360 | |||
| αE262Cβγδ | 51,300 ± 5500 | 4 | 23,000 ± 2100** | 3 |
| Free solution | 76,000 ± 4000a |
nt, Not tested. The rate constant for modification of position αL263C could be better fit with a double exponential equation.
*0.01 < p < 0.05, significant;
**0.001 < p < 0.01, very significant;
***p < 0.001, extremely significant.