Towards the elucidation of the structural-functional relationship of inward rectifying K+ channel family.

With recent cDNA cloning of members of the inward rectifying K+ channel family, it was revealed that they have only 2 putative transmembrane regions with no voltage-sensor element. Based on the deduced primary structure, possible schematic models to explain their characteristic features are proposed in this article. The features are (1) blocking by intracellular Mg2+, (2) intrinsic gating, (3) the triple barrel structure of the inward rectifier K+ channel and (4) the activation by the direct interaction with G-protein subunits of the muscarinic K+ channel. The recent findings of the mutagenesis study of voltage-gated K+ channels, which provide a clue for the structural-functional study of the inward rectifying K+ channels, are also looked at.