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Ion channel activity of a synthetic peptide with a primary structure corresponding to the presumed pore-forming region of the voltage dependent potassium channel.

A 26-mer peptide of which the sequence contains the presumed pore forming region of the Shaker K+ channel (H5 region) was chemically synthesized. The peptide was found to interact and penetrate lipid membranes based on the fluorescence of Trp residues of the peptide in the presence and absence of liposomes. The secondary structure and the ion channel forming ability of the peptide were measured by CD spectroscopy and by a planar bilayer technique, respectively. The secondary structure of the peptide was composed of a mixture of an alpha-helix, beta-sheet, beta-turn, and a random coil. The content of beta-sheet structure was increased by the presence of liposomes. In planar bilayers, the peptide formed anion-selective ion channels with a larger conductance than that of the native Shaker K+ channel. These results suggest that the H5 region of the Shaker K+ channel can penetrate into lipid bilayers and form ion channel structures by itself, but it requires other structural components to reproduce the native characteristics of the K+ channel.