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Publication Abstract from PubMed

Selective ion conduction across ion channel pores is central to cellular physiology. To understand the underlying principles of ion selectivity in tetrameric cation channels, we engineered a set of cation channel pores based on the nonselective NaK channel and determined their structures to high resolution. These structures showcase an ensemble of selectivity filters with a various number of contiguous ion binding sites ranging from 2 to 4, with each individual site maintaining a geometry and ligand environment virtually identical to that of equivalent sites in K(+) channel selectivity filters. Combined with single channel electrophysiology, we show that only the channel with four ion binding sites is K(+) selective, whereas those with two or three are nonselective and permeate Na(+) and K(+) equally well. These observations strongly suggest that the number of contiguous ion binding sites in a single file is the key determinant of the channel's selectivity properties and the presence of four sites in K(+) channels is essential for highly selective and efficient permeation of K(+) ions.

Tuning the ion selectivity of tetrameric cation channels by changing the number of ion binding sites.,Derebe MG, Sauer DB, Zeng W, Alam A, Shi N, Jiang Y Proc Natl Acad Sci U S A. 2010 Dec 27. PMID:21187421^[1]

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