Figure 9.

Mouse β3b' produces weaker instantaneous outward current rectification than human β3b. In A, tail currents at voltages from +180 through −180 mV following an activating voltage step to +180 mV are shown for α+mβ3b' currents. (B) Tail currents measured immediately following the repolarizing step are plotted for Slo1 α alone (black circles), α+mβ3b' (red circles), and α+hβ3b (black diamonds, following trypsin-mediated removal of hβ3b-mediated inactivation) with currents normalized to the amplitude at +100 mV. (C) Openings of single α+mβ3b' channels are shown at potentials from +160 to −160 mV. O and C indicate open and closed current levels, respectively. Ca²⁺ was varied from 0 μM (+160 and +100 mV), 10 μM (−100 mV), and 300 μM (−160 mV) to obtain a sufficient number of openings at each voltage. The dotted lines correspond to a 200-pS single channel conductance level. (D) Single channel currents were plotted as a function of voltage (red circles), while the instantaneous tail current amplitudes, normalized to the single channel current level at +100 mV is also shown (open circles).