Inactivation and resistance to IbTX block and conserved Cys in the mβ3a extracellular loop. (A–I) Macroscopic current conducted by pWT BK α with or without pWT or mutant mβ3a in response to step depolarizations from −80 to +140 mV. The recordings were made in outside-out macropatches with 10 µM Ca2+ inside the pipette. (J) Fraction of current remaining at the end of a 500-ms depolarizing step to +160 mV. Mean ± SEM; n = 4–6. (K) Normalized current conducted by either pWT BK α alone (no mβ3a) or pWT BK α plus pWT mβ3a before and after 100 nM IbTX. Recordings were made in outside-out macropatches. Data are means ± SEM; n ≥ 3. (L and M) Normalized current conducted by pWT BK α plus either pWT mβ3a or mutant mβ3a before and after 100 nM IbTX. Recordings were made in outside-out macropatches. Mean ± SEM; n ≥ 3.
