Figure 2. Unitary current analysis of BK in the presence of the $\mathbf{\gamma }1$ subunit reveals changes in the open-close equilibrium.

(A) Unitary recordings for hundreds of channels for $\text{BK}(\alpha +\gamma 1)$ and (B) $\text{BK}\left(\alpha \right)$ recorded in inside-out membrane patches at the indicated voltages and under symmetric 110 mM ${\text{K}}^{+}$ conditions and zero μM free internal ${\text{Ca}}^{2+}$. All-point histograms were constructed using 10–20 s of the single-channel recordings on the left, as shown in (C) $\text{BK}(\alpha +\gamma 1)$ and (D) $\text{BK}\left(\alpha \right)$. (E) Open probabilities at extreme negative voltages for $\text{BK}\left(\alpha \right)$ (blue, N = 5) and $\text{BK}\left(\alpha \right)+\gamma 1$ (purple, N = 11) were fitted to the straight-line $\text{ln}\left(\text{Po}\right)=\text{ln}\left(\text{Lo}\right)+{\text{z}}_{\text{L}}\text{FV}/\text{RT}$ with the following parameters for $\text{BK}\left(\alpha \right):{\text{L}}_0=4.9\cdot {10}^{-6}\pm 0.9\cdot {10}^{-6}y$ ${\text{z}}_{\text{L}}=0.36\pm 0.06$ while for $\text{BK}(\alpha +\gamma 1):{\text{L}}_0=4.5\cdot {10}^{-4}\pm 2.9\cdot {10}^{-4}\text{y}$ ${\text{z}}_{\text{L}}=0.74\pm 0.06$.