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. fr om genomic DNA of mouse; the gene is intronless. 2. The IRK1 gene can be stably expressed in murine erythroleukaemia (MEL) cells. Such trans fected cells show inward rectification under whole-cell recording. 3. Channels encoded by the IRK1 gene have an intrinsic gating that depend s on voltage and [Kf],. Rate constants are reduced e-fold as the drivi ng force on K+(V-E(K)) is reduced by 24.1 mV. 4. Removal of intracellu lar Mg2+ permits brief outward currents under depolarization. The inst antaneous current-voltage relation may be fitted by an appropriate con stant field expression. 5. Removal of intracellular Mg2+ speeds channe l closure at positive voltages. In nominally zero [Mg2+](i), rate cons tants for the opening and closing of channels, processes which are fir st order, are similar to those of native channels.