Characterization of the GABA-activated currents of the single Cys mutants
| EC50 (μm) | nH | Imax (nA) | n | |
|---|---|---|---|---|
| WT Cys-light | 4.0 ± 0.9 | 1.5 ± 0.1 | 4350 ± 240 | 4 |
| α1I223C | 20 ± 4 | 1.2 ± 0.2 | 560 ± 320 | 3 |
| α1G224C | 15 ± 5 | 0.8 ± 0.2 | 2100 ± 570 | 3 |
| α1Y225C | 2.0 ± 0.5 | 1.7 ± 0.3 | 4500 ± 1030 | 3 |
| α1F226C | 2.7 ± 0.4 | 1.7 ± 0.1 | 1700 ± 190 | 5 |
| α1V227C | 2.2 ± 0.4 | 1.2 ± 0.05 | 1800 ± 450 | 3 |
| α1I228C | 1.6 ± 0.3 | 0.7 ± 0.2 | 5780 ± 220 | 6 |
| α1Q229C | 2.0 ± 1.0 | 1.1 ± 0.4 | 3860 ± 290 | 5 |
| α1T230C | 16 ± 3.5 | 1.1 ± 0.1 | 2430 ± 250 | 3 |
| α1Y231C | a | a | 20 nA at 200 μm | 5 |
| α1L232C | 1.5 ± 0.5 | 0.9 ± 0.2 | 2670 ± 260 | 3 |
| β2M286C | 15 | 1.2 | ||
| β2F289C | 3.5 ± 0.75 | 1.5 ± 0.11 | 1700 ± 260 | 3 |
GABA concentration–response relationships were determined by measuring the currents induced by sequential application of increasing concentrations of GABA to oocytes expressing the single Cys mutants in α1β2γ2 receptors. α1 and β2 subunits were the Cys-light versions. Currents were normalized to the maximal current and fitted by nonlinear regression to the Hill equation. EC50 is the GABA concentration inducing half-maximal responses, nH is the Hill coefficient, and Imax is the maximal GABA-induced current. Means ± SEM are given. n, Number of oocytes tested. Data for β2M286C are from Bali and Akabas (2004).
↵aCurrents too small to determine EC50.