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. 2018 Dec 11;7:e40664. doi: 10.7554/eLife.40664

Figure 3. Co-expression with β subunits.

(a) β1 subunits have been shown to directly regulate VSD function, shifting Vh(j) to more negative values (b) Left panel, G-V curves obtained at several Ca2+concentrations after co-expression of BK667CY with the β1 subunit, which induces a leftward shift in the E-V curves obtained simultaneously (right). (c) β3bNβ1 chimeras produce similar effects to β1 on VSD function, since they retain the N-terminal region of β1 (Castillo et al., 2015). (d) G-V (left) and E-V curves (right) of BK667CY α subunits co-expressed with the β3bNβ1 chimera. Data corresponding to each Ca2+ concentration are color-coded as indicated in the legend at the bottom. Colored dashed lines represent the G-V and E-V curves corresponding to BK667CYα channels (Miranda et al., 2013; Miranda et al., 2016). The solid curves in the G-V graphs represent Boltzmann fits. The full range of G-V curves from 0 μM Ca2+ to 95 µM Ca2+ from BK667CY is represented as a grey shadow in left panels (b and d), for reference. Data points and error bars represent average ± SEM (n = 3–10; N = 2–4).

Figure 3.

Figure 3—figure supplement 1. Co-expression with β3b subunits.

Figure 3—figure supplement 1.

(a) Representative currents obtained after applying depolarizing pulses to inside-out patches expressing BK667CYα (left) or BK667CYα + β3b channels, in the presence of 12 μM Ca2+. (b) Left panel, G-V curves obtained at several Ca2+concentrations after co-expression of BK667CY with β3b subunits, inducing no appreciable changes in the E-V curves obtained simultaneously (right). Note that when β3b is co-expressed with the BK667CY construct, the kinetics of inactivation are different than those observed with wild-type BK channels (Xia et al., 2000). At first glance, it appears as if the off rate of inactivation is largely increased. Note also that there is a substantial current reduction at the tails as blockade increased with very positive potentials, which is not observed with wild-type BK channels. The simplest interpretation is that the insertion of the fluorescent protein interferes with the kinetics of blockade mediated by the β3b NH2-terminal region (Lingle et al., 2001). Understanding this discrepancy will require further study.