Primary structure and functional expression of a mouse inward rectifier K+ channel and a rat G-protein-coupled muscarinic K+ channel.

Abstract

A cDNA encoding an inward rectifier K+ channel (IRK1) was isolated by expression cloning. This channel conducts inward K+ current below the K+ equilibrium potential but passes little outward K+ current. By sequence homology with IRK1, a cDNA for a muscarinic K+ channel, another inward rectifying K+ channel which is activated by direct interaction with G-protein was isolated. In contrast with the voltage-gated K+ channels which have six transmembrane segments, the IRK1 channel and the GIRK1 channel contains only two putative transmembrane segments per subunit and corresponds to the inner core structure of voltagegated K+ channels. The IRK1 channel and the GIRK1 channel show extensive sequence similarity and constitute a new superfamily.