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Publication Abstract from PubMed

Inward rectifier K(+) (Kir) channels are activated by phosphatidylinositol-(4,5)-bisphosphate (PIP(2)), but G protein-gated Kir (K(G)) channels further require either G protein betagamma subunits (Gbetagamma) or intracellular Na(+) for their activation. To reveal the mechanism(s) underlying this regulation, we compared the crystal structures of the cytoplasmic domain of K(G) channel subunit Kir3.2 obtained in the presence and the absence of Na(+). The Na(+)-free Kir3.2, but not the Na(+)-plus Kir3.2, possessed an ionic bond connecting the N terminus and the CD loop of the C terminus. Functional analyses revealed that the ionic bond between His-69 on the N terminus and Asp-228 on the CD loop, which are known to be critically involved in Gbetagamma- and Na(+)-dependent activation, lowered PIP(2) sensitivity. The conservation of these residues within the K(G) channel family indicates that the ionic bond is a character that maintains the channels in a closed state by controlling the PIP(2) sensitivity.

A structural determinant for the control of PIP2 sensitivity in G protein-gated inward rectifier K+ channels.,Inanobe A, Nakagawa A, Matsuura T, Kurachi Y J Biol Chem. 2010 Dec 3;285(49):38517-23. Epub 2010 Sep 29. PMID:20880843^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.