TABLE II.
Effects of Various Extracellular MTS Reagents on the Gating of Three Cysteine Mutants
| G-V | Inactivation | Steady-state inactivation | ||||||
|---|---|---|---|---|---|---|---|---|
| V0.5 | δ | n | τh, −40 mV | n | V0.5 | δ | n | |
| mV | ms | mV | ||||||
| L1433C | −41.2 ± 0.6 | 4.10 ± 0.09 | 14 | 1.69 ± 0.08 | 14 | −78.0 ± 0.7 | 4.09 ± 0.11 | 13 |
| MTSESext | −41.8 ± 0.8 | 4.15 ± 0.15 | 8 | 3.85 ± 0.11b | 8 | −69.4 ± 1.2b | 3.26 ± 0.06b | 8 |
| MTSEText | −43.8 ± 0.5b | 4.04 ± 0.26 | 5 | 4.47 ± 0.16b | 5 | −72.1 ± 1.6a | 3.24 ± 0.07b | 3 |
| S1427C | −38.2 ± 0.6 | 3.72 ± 0.04 | 25 | 2.08 ± 0.05 | 25 | −76.8 ± 0.5 | 3.75 ± 0.09 | 25 |
| MTSESext | −44.0 ± 1.3b | 3.11 ± 0.09b | 7 | 1.13 ± 0.05b | 7 | −100.9 ± 1.5b | 2.70 ± 0.07b | 7 |
| MTSEText | −38.0 ± 3.6 | 2.69 ± 0.22a | 3 | 1.52 ± 0.09b | 5 | −92.3 ± 0.6b | 3.20 ± 0.13b | 5 |
| BPMTSext | −39.4 ± 1.6 | 3.15 ± 0.09b | 4 | 1.11 ± 0.06b | 5 | −104.0 ± 1.8b | 1.97 ± 0.06b | 5 |
| D1420N/S1427C | −35.1 ± 0.5 | 3.78 ± 0.08 | 20 | 2.58 ± 0.07 | 25 | −81.1 ± 0.6 | 3.52 ± 0.04 | 24 |
| MTSESext | −41.6 ± 1.4b | 3.72 ± 0.20 | 6 | 1.57 ± 0.08b | 6 | −97.4 ± 0.6b | 2.45 ± 0.05b | 7 |
| MTSEText | −37.4 ± 1.3 | 2.78 ± 0.06b | 9 | 2.30 ± 0.13 | 11 | −94.4 ± 0.8b | 2.64 ± 0.08b | 11 |
Not apparent from this table is the small but significant perturbation of fast inactivation in D1420N/S1427C by MTSET, which decreased τh at hyperpolarized voltages (e.g., −50 mV) and increased τh at depolarized voltages (e.g., 30 mV). Thus, in these three selected mutants, all extracellular MTS reagents appeared to affect both fast inactivation and steady state inactivation. Data are presented as mean ± SEM (n).
a
P < 0.05. bP < 0.01.