Ion channels are integral membrane proteins. A hollow centre through the channel protein forms a water-filled pore through which ions permeate. Ion channels are referred to by the type of permeating ion. K+ channels specifically allow potassium ions to cross the cell membrane through a water-filled channel protein.
Biophysical and biochemical analyses suggested that voltage-gated and inward rectifier K+ channel protein complexes exist as tetrameric structures, consisting of four separate pore forming or principal subunits (also called alpha-subunits) arranged symmetrically around a central pore. This tetrameric channel structure was recently confirmed experimentally with the crystallization and high-resolution structural analysis of a prokaryotic K+ channel from Streptomyces lividans (Doyle et al., 1998) - the first natural membrane channel for which high resolution structural information became available. In addition to these principal subunits, many K+ channel protein complexes also contain auxiliary proteins (sometimes also referred to as beta-subunits) that can significantly modify the properties of the channel complex.
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Last updated: March 9, 2003
Based on data as published in: Coetzee, W.A., Y. Amarillo, J. Chiu, A. Chow, T. McCormack, H. Moreno, M. Nadal, A. Ozaita, D. Pountney, E. Vega-Saenz de Miera, and B. Rudy. Molecular Diversity of K+ Channels. In: Molecular and Functional Diversity of Ion Channels and Receptors, edited by B. Rudy and P. Seeburg. New York: New York Academy of Sciences, 1999. [Download PDF file]