A novel potassium channel with delayed rectifier properties isolated from rat brain by expression cloning

Abstract

VOLTAGE-activated potassium channels play an important part in the control of excitability in nerve and muscle. Different K+ channels are involved in establishing the resting potential, deter-mining the duration of action potentials, modulation of transmitter release, and in rhythmic firing patterns and delayed excitation1. Using in vitro transcripts made from a directional complementary DNA library we have isolated, by expression cloning in Xenopus oocytes, a novel K+-channel gene (drk1). Functionally, drk1 encodes channels that are K+ selective and belong to the delayed rectifier class of channels, rather than the A-type class encoded by the Shaker gene of Drosophila. The channels show sigmoidal voltage-dependent activation and do not inactivate within 500 ms. Structurally, drk1 encodes an amino-acid sequence which is more closely related to the Drosophila Shab gene than to the Shaker gene.