Conformation and ion channel properties of a five-helix Bundle protein.
The primary amphipathic peptide Ac-Met-Gly-Leu-Gly-Leu-Trp-Leu-Leu-Val-Leu10-Ala-Ala-Ala-Leu-Gln-Gly-Ala-Lys-Lys-Lys20-Arg-Lys-Val-NH-CH2-CH2-SH called SPM was able to induce formation of ion channels into planar lipid bilayers with main conductance values of 75 and 950 pS in 1 M KCl. The 75 pS value can be attributed to an aggregate composed of five monomers since the corresponding five-unit bundle (5-SPM) also presented a 70 pS channels under the same conditions. The upper 950 pS level would be generated by a hexameric aggregate. Ion channels induced by both SPM and its pentameric bundle are slightly cation selective but not voltage-dependent. The structural studies showed that the SPM and 5-SPM possess mainly an alpha-helical structure (approximately 40%) and are strongly embedded in the bilayer. This behaviour and the strong hydrophobic interactions occurring between helices in the bundle induce a strong stabilization of 5-SPM in the bilayer and would be responsible for the stepwise current fluctuations observed during the incorporation of 5-SPM into the membrane.
UMR 6522 CNRS, IFRMP 23, Faculté des Sciences, Mont-Saint-Aignan, France.
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D000465:Algorithms; D000595:Amino Acid Sequence; D002942:Circular Dichroism; D007473:Ion Channels / Q000737:chemistry*; D008051:Lipid Bilayers; D009682:Magnetic Resonance Spectroscopy; D008564:Membrane Potentials; D008954:Models, Biological; D010446:Peptide Fragments / Q000737:chemistry; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry*; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence
D007473:Ion Channels; D008051:Lipid Bilayers; D010446:Peptide Fragments; D010455:Peptides