TABLE 1.
Effect of Lqh2 and LqhαIT on channel mutants
The channels were clamped at a holding potential of −80 mV, and currents were elicited by depolarization to −20 mV in the presence of increasing toxin concentrations. At each toxin concentration, the currents were allowed to reach a steady-state level prior to the final measurement. Determination of dose-dependent effect of the toxin (removal of fast inactivation) is described in detail under “Experimental Procedures”, and the EC50 values provided are mean ± S.E., where n stands for the number of cells analyzed. No effect denotes lack of effect on channel inactivation in the presence of 5 μm toxin.
| Channel derivative | EC50 of Lqh2 | EC50 of LqhαIT |
|---|---|---|
| nm | nm | |
| DmNav1 unmodified | 6920 ± 1420 | 0.36 ± 0.04 |
| DmNav1D1701E | >5000 (n = 3) | 50 ± 4.1 (n = 3) |
| DmNav1D1701R | No effect | No effect |
| DmNav1rNav1.2a(DIV/S1-S2) | 1530 ± 433 (n = 4) | 3.2 ± 0.6 (n = 5) |
| DmNav1rNav1.2a(DIV/S1-S2+S3-S4) | 120 ± 12 (n = 5) | 57 ± 17 (n = 3) |
| DmNav1rNav1.2a(DIV/S3-MFLA) | 495 ± 113 (n = 3) | 1.4 ± 0.1 (n = 3) |
| DmNav1rNav1.2a(DI/S5-SS1) | >2500 (n = 3) | 0.65 ± 0.1 (n = 3) |
| DmNav1rNav1.2a(DI/SS2-S6) | >5000 (n = 3) | 0.54 ± 0.06 (n = 2) |
| DmNav1rNav1.2a(D1/S5-SS1+SS2-S6) | 123 ± 26 (n = 3) | 0.48 ± 0.12 (n = 3) |
| DmNav1rNav1.2a(site-3 face)a | 26.7 ± 3.1 (n = 5) | 241 ± 47 (n = 4) |
| DmNav1rNav1.2a(site-3 face-E1613D) | 22.5 ± 1.9 (n = 3) | 0.37 ± 0.03 (n = 4) |
| rNav1.2aE1613D | 14.5 ± 5.7 (n = 4) | 18.8 ± 3.3 (n = 4) |
| rNav1.2a unmodified | 13.6 ± 1.4 (n = 3) | 17,800 ± 357 (n = 5) |
a Site-3 face denotes DI/S5-SS1+SS2-S6, DIV/S1-S2+S3-S4 exchanged in DmNav1 by their rNav1.2a equivalents.