Defining the conductance of the closed state in a voltage-gated K+ channel.
The opening and closing of the ion conduction pathway in ion channels underlies the generation and propagation of electrical signals in biological systems. Although electrophysiological approaches to measuring the flow of ions in the open state have contributed profoundly to our understanding of ion permeation and gating, it remains unclear how much the ion-throughput rate decreases upon closure of the ion conduction pore. To address this fundamental question, we expressed the Shaker Kv channel at high levels and then measured macroscopic K+ currents at negative membrane voltages and counted the number of channels by quantifying the translocation of gating charge. Our results show that the conductance of the closed state is between 0 and 0.16 fS, or at least 100,000 times lower than for the open state of the channel, indicating that the flow of ions is very tightly regulated in this class of K+ channels.
Soler-Llavina
Gilberto J
GJ
Molecular Physiology and Biophysics Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.
Holmgren
Miguel
M
Swartz
Kenton J
KJ
D000818:Animals; D004330:Drosophila; D029721:Drosophila Proteins; D004553:Electric Conductivity; D015640:Ion Channel Gating / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000737:chemistry / Q000502:physiology*; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D051637:Shaker Superfamily of Potassium Channels; D014982:Xenopus laevis
D029721:Drosophila Proteins; D015221:Potassium Channels; C496929:Sh protein, Drosophila; D051637:Shaker Superfamily of Potassium Channels; D011188:Potassium