Inactivation of Kv2.1 potassium channels.
We report here several unusual features of inactivation of the rat Kv2.1 delayed rectifier potassium channel, expressed in Xenopus oocytes. The voltage dependence of inactivation was U-shaped, with maximum inactivation near 0 mV. During a maintained depolarization, development of inactivation was slow and only weakly voltage dependent (tau = 4 s at 0 mV; tau = 7 s at +80 mV). However, recovery from inactivation was strongly voltage dependent (e-fold for 20 mV) and could be rapid (tau = 0.27 s at -140 mV). Kv2.1 showed cumulative inactivation, where inactivation built up during a train of brief depolarizations. A single maintained depolarization produced more steady-state inactivation than a train of pulses, but there could actually be more inactivation with the repeated pulses during the first few seconds. We term this phenomenon "excessive cumulative inactivation." These results can be explained by an allosteric model, in which inactivation is favored by activation of voltage sensors, but the open state of the channel is resistant to inactivation.
Klemic
K G
KG
Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio 44106, USA. kxg13@po.cwru.edu
Shieh
C C
CC
Kirsch
G E
GE
Jones
S W
SW
D000494:Allosteric Regulation; D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D051668:Delayed Rectifier Potassium Channels; D005260:Female; D066298:In Vitro Techniques; D007700:Kinetics; D008564:Membrane Potentials; D008954:Models, Biological; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D051381:Rats; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors; D051669:Shab Potassium Channels; D014981:Xenopus
D051668:Delayed Rectifier Potassium Channels; C496991:Kcnb1 protein, rat; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D011994:Recombinant Proteins; D051669:Shab Potassium Channels