Fig. 5.

Cross-linking indicates that βE153C and βK196C are spatially proximal and that agonist activation (GABA or PB) limits the mobility of loop C. (A) GABA concentration-response curves from oocytes expressing WT α1β2γ2S (open squares, dashed line), α1β2E153Cγ2S (filled triangles), α1β2K196Cγ2S (inverted filled triangles), and α1β2E153C-K196Cγ2S (filled diamonds) receptors. (B) Percentage of inhibition of I_GABA or I_PB for WT and mutant receptors after promoting cysteine cross-linking with 0.3% H₂O₂ for 3 min in the presence and absence of GABA or PB. Data are mean ± SEM from at least three experiments and at least two batches of oocytes. (Inset) Current traces from an oocyte expressing α1β2E153C-K196Cγ2S receptor during a cross-linking experiment. The inhibition of GABA current amplitude after application of 0.3% H₂O₂ is reversed by 10 mM DTT (3 min). *, values are significantly different from WT, P < 0.05 (one-way ANOVA).