Table 2.
Characteristics of [3H]muscimol binding to wild-type and cysteine-substituted GABAA receptors
| Receptor | KD(nm) | KMUT/KWT | n |
|---|---|---|---|
| αβ | 62 ± 5 | 1.0 | 22 |
| αY59Cβ | 177 ± 21 | 2.9 | 2 |
| αT60Cβ | 142 ± 30 | 2.3 | 5 |
| αI61Cβ | 129 ± 8 | 2.1 | 3 |
| αD62Cβ | L.B. | 3 | |
| αV63Cβ | 89 ± 15 | 1.4 | 5 |
| αF64Cβ | L.B. | 3 | |
| αF65Cβ | L.B. | 5 | |
| αR66Cβ | L.B. | 3 | |
| αQ67Cβ | No significant binding | 3 | |
| αS68Cβ | 65 ± 8 | 1.1 | 3 |
| αW69Cβ | No significant binding | 3 |
The affinity of muscimol binding to wild-type and mutant receptors was determined by [3H]muscimol saturation and competition binding assays as described in Materials and Methods. The means and SEM are shown for n independent experiments, each with triplicate determinations. Cysteine substitution of α1 Y59, T60, I61, V63, or S68 had little effect on muscimol affinity. L.B., Low levels of specific binding made it difficult to accurately determine the affinity of muscimol binding to these mutant receptors.