Tuning the ion selectivity of tetrameric cation channels by changing the number of ion binding sites.Derebe, M.G., Sauer, D.B., Zeng, W., Alam, A., Shi, N., Jiang, Y.
(2011) Proc.Natl.Acad.Sci.USA 108: 598-602
- PubMed: 21187421
- DOI: 10.1073/pnas.1013636108
- Primary Citation of Related Structures:
- PubMed Abstract:
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 c ...
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.
Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9040, USA.