TABLE 2.
Second order rate constants in the absence and presence of propofol
Propofol slowed the rate of modification of L240C (intersubunit cavity) and increased the rate of modification of T254C. Rates were measured at pH 7.6 (resting state) except for T254C, for which rates were also measured at pH 6.5 (activated/desensitized). Data are the mean ± S.E. from n experiments.
| Channel | pH | Location | Reagent |
k2 |
p | |
|---|---|---|---|---|---|---|
| −Propofol | +Propofol | |||||
| m−1s−1 | ||||||
| I201C (M1) | 7.6 | Intra | MTSEA | 3.3 ± 0.4 (n = 4) | 3.1 ± 0.7 (n = 3) | 0.821 |
| N238C (M2 15′) | 7.6 | Inter | MMTS | 22.3 ± 3.0 (n = 6) | 20.7 ± 5.0 (n = 5) | 0.778 |
| L240C (M2 17′) | 7.6 | Inter | pCMBS | 907 ± 66.6 (n = 8) | 634 ± 71.5 (n = 9)a | 0.014 |
| MTSEA | 324 ± 31.0 (n = 5) | 161 ± 19.7 (n = 5)b | 0.002 | |||
| V241C (M2 18′) | 7.6 | Intra | MTSEA | k′ = 16.0 ± 2.8 (n = 5) | k′ = 14.7 ± 4.8 (n = 3) | 0.774 |
| k″ = 29.8 ± 6.15 (n = 5) | k″ = 22.6 ± 5.5 (n = 3) | 0.459 | ||||
| E242C (M2 19′) | 7.6 | Inter | MTSEA | 9.0 × 104 ± 1.0 × 104 (n = 4) | 8.9 × 104 ± 1.9 × 104 (n = 5) | 0.991 |
| T243C (M2 20′) | 7.6 | Pore | MTSEA | 1.2 × 105 ± 3.7 × 103 (n = 3) | 1.3 × 105 ± 7.3 × 103 (n = 3) | 0.513 |
| T254C (M3) | 7.6 | Intra | MTSEA | 374.1 ± 25.1 (n = 4) | 1267.0 ± 171.4 (n = 4)b | 0.002 |
| 6.5 | MTSEA | 70.0 ± 12.8 (n = 5) | 140.0 ± 16.6 (n = 5) a | 0.01 | ||
a Rates in the presence of propofol were significantly different than those in its absence; p < 0.05.
b Rates in the presence of propofol were significantly different than those in its absence; p < 0.01.