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The conformational analysis of a synthetic S4 peptide corresponding to a voltage‐gated potassium ion channel protein
Author(s) -
Haris Parvez I.,
Ramesh Bala,
Brazier Stephen,
Chapman Dennis
Publication year - 1994
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(94)00704-7
Subject(s) - random coil , chemistry , peptide , micelle , voltage gated potassium channel , aqueous solution , lipid bilayer , bilayer , circular dichroism , crystallography , biophysics , membrane , biochemistry , potassium , organic chemistry , biology
The S4 region of the Drosophila Shaker voltage‐gated K + channel has been proposed to function as a voltage‐sensor. We have synthesised a peptide corresponding to this S4 region. Structural studies on the S4 peptide were conducted using Fourier transform infrared (FTIR) spectroscopy. Spectra were obtained for the peptide dissolved in aqueous solution, in trifluoroethanol solvent and also after reconstitution into lipid bilayers and micelles. The peptide in trifluoroethanol adopts an α‐helical conformation which is in good agreement with the results of a recent 2D NMR study on the structure of a S4 peptide corresponding to the rat brain sodium channel [(1989) FEBS Lett. 257, 113‐1171. A predominantly α‐helical structure is also observed when the S4 peptide is present in aqueous lysophosphatidylcholine micelles, in dimyristoyl phosphatidylcholine and dimyristoyl phosphatidylglycerol lipid bilayers. In contrast to this, the S4 peptide in aqueous solution is in a random coil conformation. The coil‐to‐helix transition observed for the S4 peptide upon its transfer from aqueous solution to lipid membrane indicates that it has a high degree of conformational flexibility and can undergo large changes in its structure in response to its environment. This may have important implications for its role in the voltage activation process during which the S4 peptide has been postulated to, at least partially, move from a lipid bilayer to an aqueous extracellular media [(1992) Biophys J. 62, 238 250]. The results of our study lend support to such a model.