InterPro domain: IPR040445

Inwardly-rectifying potassium channels (Kir) are the principal class of two-TM domain potassium channels. They are characterised by the property of inward-rectification, which is described as the ability to allow large inward currents and smaller outward currents. Inwardly rectifying potassium channels (Kir) are responsible for regulating diverse processes including: cellular excitability, vascular tone, heart rate, renal salt flow, and insulin release [ 1 ]. To date, around twenty members of this superfamily have been cloned, which can be grouped into six families by sequence similarity, and these are designated Kir1.x-6.x [ 2 , 3 ].

Cloned Kir channel cDNAs encode proteins of between ~370-500 residues, both N- and C-termini are thought to be cytoplasmic, and the N terminus lacks a signal sequence. Kir channel alpha subunits possess only 2TM domains linked with a P-domain. The two 'transmembrane passes' place the C-terminal tail on the cytoplasmic side of the membrane [ 4 ]. It is thought that four Kir subunits assemble to form a tetrameric channel complex, which may be hetero- or homomeric [ 4 ].

1. Transmembrane structure of an inwardly rectifying potassium channel. Cell 96, 879-91
2. The inward rectifier potassium channel family. Curr. Opin. Neurobiol. 5, 268-77
3. Inwardly rectifying potassium channels. Curr. Opin. Cell Biol. 11, 503-8