The intrinsic gating of inward rectifier K+ channels expressed from the murine IRK1 gene depends on voltage, K+ and Mg2+.
1. We describe the cloning of the inward rectifier K+ channel IRK1 from genomic DNA of mouse; the gene is intronless. 2. The IRK1 gene can be stably expressed in murine erythroleukaemia (MEL) cells. Such transfected cells show inward rectification under whole-cell recording. 3. Channels encoded by the IRK1 gene have an intrinsic gating that depends on voltage and [K+]o. Rate constants are reduced e-fold as the driving force on K+(V-EK) is reduced by 24.1 mV. 4. Removal of intracellular Mg2+ permits brief outward currents under depolarization. The instantaneous current-voltage relation may be fitted by an appropriate constant field expression. 5. Removal of intracellular Mg2+ speeds channel closure at positive voltages. In nominally zero [Mg2+]i, rate constants for the opening and closing of channels, processes which are first order, are similar to those of native channels.
Stanfield
P R
PR
Department of Cell Physiology and Pharmacology, University of Leicester.
Davies
N W
NW
Shelton
P A
PA
Khan
I A
IA
Brammar
W J
WJ
Standen
N B
NB
Conley
E C
EC
D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D003001:Cloning, Molecular; D004594:Electrophysiology; D016678:Genome; D007438:Introns; D015640:Ion Channel Gating / Q000502:physiology*; D004915:Leukemia, Erythroblastic, Acute / Q000378:metabolism; D008274:Magnesium / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011188:Potassium / Q000502:physiology*; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*
D015221:Potassium Channels; D008274:Magnesium; D011188:Potassium