In Figure 4 Ca, we show normalized simulated traces for WT and the mutants generated for the mean values of the rate constants presented in Figure 4 Da, for the 30 ms time window. Taken altogether, the α 1 G258V and β 2 L296V mutations showed a clear trend to impair late gating transitions (opening/closing and desensitization), having little or no effect on binding and preactivation.
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Mutations at the M2 and M3 Transmembrane Helices of the GABA<sub>A</sub>Rs α<sub>1</sub> and β<sub>2</sub> Subunits Affect Primarily Late Gating Transitions Including Opening/Closing and Desensitization.
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Taken together, except for the β 2 G254V mutation, which did not affect single-channel openings in all the remaining mutants, an overall trend to shorten the open times was observed, suggesting an increased closing rate compared to that of the WT receptors.
There was a slight trend to accelerate the current onset in the β 2 G254V mutant; however, it was not significant, and importantly, recordings for this receptor were made in the lifted-cell mode in which solution exchange is markedly slower than in the case of excised-patches (compare RT for WT: 0.41 and 1.83 ms in excised-patch and lifted-cell, respectively; Figure 3 A,B; Table 1 ).