Multiple PIP2 binding sites in Kir-2.1 inwardly rectifying potassium channels

Inwardly rectifying potassium channels require binding of phosphatidylinosi tol-4,5-bisphosphate (PIP2) for channel activity. Three independent sites ( aa 175-206, aa 207-246, aa 324-365) were located in the C-terminal domain o f Kir2.1 channels by assaying the binding of overlapping fragments to PIP2 containing liposomes. Mutations in the first site, which abolished channel activity, reduced PIP2 binding of this fragment but not of the complete C-t erminus, Point mutations in the third site also reduced both, channel activ ity and PIP2 binding of this segment. The relevance of the third PIP2 bindi ng site provides a basis for the understanding of constitutively active Kir 2 channels. (C) 2001 Federation of European Biochemical Societies, Publishe d by Elsevier Science B.V. All rights reserved.