Biophysical Journal
Volume 100, Issue 5, 2 March 2011, Pages L28-L30
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Letter
Properties of Deactivation Gating Currents in Shaker Channels

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Abstract

The charge versus voltage relation of voltage-sensor domains shifts in the voltage axis depending on the initial voltage. Here we show that in nonconducting W434F Shaker K+ channels, a large portion of this charge-voltage shift is apparent due to a dramatic slowing of the deactivation gating currents, IgD (with τ up to 80 ms), which develops with a time course of ∼1.8 s. This slowing in IgD adds up to the slowing due to pore opening and is absent in the presence of 4-aminopyridine, a compound that prevents the last gating step that leads to pore opening. A remaining 10–15 mV negative shift in the voltage dependence of both the kinetics and the charge movement persists independently of the depolarizing prepulse duration and remains in the presence of 4-aminopyridine, suggesting the existence of an intrinsic offset in the local electric field seen by activated channels. We propose a new (to our knowledge) kinetic model that accounts for these observations.

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