Fig. 4.

Activation of Slo, dependent on voltage and Ca²⁺, is slowed by β₄ and β₁. A: current traces of inside-out macropatches from oocytes injected with cSlo, cSlo and β₁, and cSlo and β₄ cRNA subjected to a step voltage protocol. Patches were held at −100 mV and stepped to a range of voltages varying from −80 to +180 mV before stepping back to −100 mV (1 μM intracellular Ca²⁺). β₄ slows activation more than β₁ (cSlo, n = 15; cSlo + β₁, n = 12; cSlo + β₄, n = 20). B: activation time constants (τ_activation) as a function of Ca²⁺ (with voltage stepped from −100 to +60 mV, top) and voltage (with intracellular Ca²⁺ held at 1 μM, bottom). As is evident, higher voltage and Ca²⁺ both result in shortened times of activation.