In vitro synthesis, tetramerization and single channel characterization of virus-encoded potassium channel Kcv

Chlorella virus-encoded membrane protein Kev represents a new class of potassium channel. This 94-amino acids miniature K+ channel consists of two trans-membrane alpha-helix domains intermediated by a pore domain that contains a highly conserved K+ selectivity filter. Therefore, as an archetypal K+ channel, the study of Kcv may yield valuable insights into the structure-function relationships underlying this important class of ion channel. Here, we report a series of new properties of Kcv. We first verified Kcv can be synthesized in vitro. By co-synthesis and assembly of wild-type and the tagged version of Kcv, we were able to demonstrate a tetrameric stoichiometry, a molecular structure adopted by all known K+ channels. Most notably, the tetrameric Kcv complex retains its functional integrity in SDS (strong detergent)-containing solutions, a useful feature that allows for direct purification of protein from polyacrylamide gel. Once purified, the tetramer can form single potassium-selective ion channels in a lipid bilayer with functions consistent to the heterologously expressed Kcv. These finding suggest that the synthetic Kcv can serve as a model of virus-encoded K+ channels; and its newly identified properties can be applied to the future study on structure-determined mechanisms such as K+ channel functional stoichiometry. (c) 2007 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.