Figure 6.

Cross-linking of β3a Cys152 in the extracellular loop to α S1–S6. (A) β3a Cys152 cross-links to native Cys, Cys14, and Cys141 in α. The fraction of endogenous cross-linking between β3a Cys152 and α Cys14 or α Cys141 is shown at the bottom of each lane. Immunoblot with anti-BK α antibody. (B) Representative macroscopic currents conducted by WT α plus pWT mβ3a, pWT α plus pWT mβ3a, C14A α plus pWT mβ3a, and C141A α plus pWT mβ3a before (black trace) and after (red trace) 100 nM IbTBX. (C) Normalized current conducted by WT α, pWTα, C14A α, or C141Aα plus pWT mβ3a before and after 100 nM IbTX. Data points are means ± SEM; n > 3. pWT α without mβ3a is shown as a dashed blue line. (D) Extents of endogenous disulfide bond formation between Cys-substituted extracellular flanks of α S0–S6 and Cys152 of pWT β3a. The α residues substituted by Cys are shown on the left. The extents of disulfide bond formation are represented by bars in the horizontal direction. In the cases in which the mean extent of disulfide bond formation was zero, the value 0.5% was plotted to identify these pairs as tested. (E–G) Normalized current conducted by P137C α with or without pWT mβ3a, G260C α with or without pWT mβ3a, and K296C α with or without pWT mβ3a before and after 100 nM IbTX. pWTα plus pWT mβ3a is shown as a dashed line. Data are means ± SEM; n ≥ 3. (Insets) Representative macroscopic currents conducted by P137C α plus pWT mβ3a, G260C α plus pWT mβ3a, and K296C α plus pWT mβ3a before (black trace) and after (red trace) 100 nM IbTX.