title: Properties of deactivation gating currents in Shaker channels.
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, Ig(D) (with τ up to 80 ms), which develops with a time course of ∼1.8 s. This slowing in Ig(D) 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.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA.
authors.forename: Jérôme J
authors.initials: JJ
authors.lastname: Lacroix
authors.forename: Alain J
authors.initials: AJ
authors.lastname: Labro
authors.forename: Francisco
authors.initials: F
authors.lastname: Bezanilla
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008954:Models, Biological; D051637:Shaker Superfamily of Potassium Channels / Q000378:metabolism*
chemical_list: D051637:Shaker Superfamily of Potassium Channels; D015761:4-Aminopyridine