Rates of MTS-ET effects on TH6–TH7 segment mutant channels
| Mutant | cis pH | mV | kcis | ktrans |
| M−1 s−1 | M−1 s−1 | |||
| T300C | 7.0 | 60 | 40 ± 13 (n = 4) | NE (n = 2) |
| T301C | 6.2 | 60 | 15 ± 2 (n = 3) | NE (n = 2) |
| A302C | 5.3 | −20 | 8.1 ± 0.2 (n = 2) | NE (n = 2) |
| A303C | 7.2 | 40–60 | 1,094 ± 91 (n = 3) | NE (n = 3) |
| L304C | 6.6 | 60 | 68 ± 9 (n = 3) | NE (n = 2) |
| S305Ca | 5.3 | 0 | 192 ± 40 | 79 ± 10 |
| I306C | 5.3 | −30 or 30b | 4.4 ± 0.8 (n = 2) | 5.6 ± 0.2 (n = 2) |
| L307C | 5.3 | 30–40 | 33 ± 9 (n = 3) | 607 ± 377 (n = 6) |
| G309C | 5.3 | 20–60 | 40 ± 19 (n = 4) | 750 ± 479 (n = 4) |
| I310Cc | 6.3 | 60 | 44 (n = 4) | <2 (n = 3) |
| S312Ca | 5.3 | 0 | 7.4 ± 1 | 11.4 ± 2 |
| V313C | 6.3 | 20–60 | 8 ± 4 (n = 4) | NE (n = 2) |
| M314C | 6.3 | 20–60 | 10 ± 4 (n = 6) | NE (n = 4) |
| G315Cc | 5.2 | 30–60 | 7 (n = 6) | <0.5 (n = 4) |
| I316C | 5.2 | 40 | 32 ± 10 (n = 3) | NE (n = 2) |
| A317C | 7.0 | 60 | 113 ± 72 (n = 3) | NE (n = 2) |
| Mutant | cis pH | mV | kcis | ktrans |
| M−1 s−1 | M−1 s−1 | |||
| T300C | 7.0 | 60 | 40 ± 13 (n = 4) | NE (n = 2) |
| T301C | 6.2 | 60 | 15 ± 2 (n = 3) | NE (n = 2) |
| A302C | 5.3 | −20 | 8.1 ± 0.2 (n = 2) | NE (n = 2) |
| A303C | 7.2 | 40–60 | 1,094 ± 91 (n = 3) | NE (n = 3) |
| L304C | 6.6 | 60 | 68 ± 9 (n = 3) | NE (n = 2) |
| S305Ca | 5.3 | 0 | 192 ± 40 | 79 ± 10 |
| I306C | 5.3 | −30 or 30b | 4.4 ± 0.8 (n = 2) | 5.6 ± 0.2 (n = 2) |
| L307C | 5.3 | 30–40 | 33 ± 9 (n = 3) | 607 ± 377 (n = 6) |
| G309C | 5.3 | 20–60 | 40 ± 19 (n = 4) | 750 ± 479 (n = 4) |
| I310Cc | 6.3 | 60 | 44 (n = 4) | <2 (n = 3) |
| S312Ca | 5.3 | 0 | 7.4 ± 1 | 11.4 ± 2 |
| V313C | 6.3 | 20–60 | 8 ± 4 (n = 4) | NE (n = 2) |
| M314C | 6.3 | 20–60 | 10 ± 4 (n = 6) | NE (n = 4) |
| G315Cc | 5.2 | 30–60 | 7 (n = 6) | <0.5 (n = 4) |
| I316C | 5.2 | 40 | 32 ± 10 (n = 3) | NE (n = 2) |
| A317C | 7.0 | 60 | 113 ± 72 (n = 3) | NE (n = 2) |
The rates are given as mean ± SD, with n being the number of macroscopic experiments, except where indicated otherwise. The trans pH was 7.2 for all experiments. The His6-tag was removed from the T-domain for the experiments with A302C, S305C, I306C, and S312C. NE, no effect.
The rates for S305C and S312C are from the fitted lines in the graphs in Fig. 6. The error range was estimated by eye.
For I306C, kcis was measured at 30 mV and ktrans was measured at −30 mV.
A trans MTS-ET effect was observed in single-channel experiments with I310C and G315C, but it was too slow to be detected in macroscopic experiments. The rates given here were estimated from the single-channel waiting times. In some of the experiments with trans MTS-ET, the channel did not react after a long waiting time, so the value given for the rate is an upper limit. Here, n is the number of reaction events.