CLONING AND EXPRESSION OF A FAMILY OF INWARD RECTIFIER POTASSIUM CHANNELS

Five new members of the two-transmembrane domain potassium channel fam ily have been identified from rat brain, heart and skeletal muscle. Th e channel mRNAs are differentially expressed and found in both the cen tral nervous system and periphery. Expression of two of these channels in Xenopus oocytes gave rise to inwardly rectifying potassium current s which were voltage-dependently blocked by barium and cesium. Voltage command pulses negative to E(k) evoked inward currents which rapidly reached a peak amplitude and relaxed to a steady-state level. The quan tity of current relaxation differed in the two channels and was increa sed at more negative potentials. The degree of current rectification w as also different for the two channels. The results demonstrate the ex istence of a large and widely expressed family of inward rectifier pot assium channel subunits with distinct tissue distributions and functio nal properties.