Figure 4.

PCMBS modulates channel kinetics. Activation and deactivation kinetics were estimated with Ca²⁺ jump experiments in the absence and presence of PCMBS. A rapid solution exchanger was used to quickly alternate between a Ca²⁺_i-free solution and one of four Ca²⁺_i solutions: (A) 0.5, (B) 0.7, (C) 1.0, and (D) 10 µM Ca²⁺_i according to the protocol illustrating one complete Ca²⁺ cycle shown in the inset of this figure. 5–10 complete Ca²⁺ cycles were recorded from a single patch in the absence and presence of PCMBS (500 µM). Activation and deactivation sweeps in the absence of PCMBS (black trace) were collected and averaged according to their respective Ca²⁺ concentration and superimposed against the corresponding PCMBS sweep (red trace). Current traces were normalized to the max current level, facilitating comparison of time courses between KCa3.1 and KCa3.1+PCMBS. Activation (E) and deactivation (F) rates were estimated by fitting activation and deactivation records with an exponential function and reported as a time constant (τ-on and τ-off) in the absence (▴) and presence (▵) of PCMBS, see also Table I.