Synthetic peptide K+ carrier with Ca2+ inhibition |
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Authors: | RJ Bradley WO Romine MM Long T Ohnishi MA Jacobs DW Urry |
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Institution: | The Neurosciences Program, University of Alabama Medical Center, Birmingham, Alabama 35294 U.S.A.;Laboratory of Molecular Biophysics and the Cardiovascular Research and Training Center, University of Alabama Medical Center, Birmingham, Alabama 35294 U.S.A. |
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Abstract: | Based on a proposed solution conformation of the Ca2+ ion complex of the repeat hexapeptide of elastin, l-Val-l-Ala-l-Pro-Gly-l-Val-Gly, it is possible to modify the molecule making it more lipophilic for lipid bilayer permeation while retaining its complexation features. Therefore the two peptides, For-MeVal-Ala-Pro-Sar-Pro-Sar-OMe and For-MeVal-Ala-Pro-Sar-Pro-Sar-OH, were synthesized and evaluated for lipid bilayer activity and cation binding (For, N-formyl; Me, N-methyl; Sar, N-methyl glycine). Both peptides bound Ca2+ preferentially but did not exhibit the properties of a Ca2+ carrier. They were however active as K+ carriers although K+ ion titration curves showed a much lower affinity for K+ than for Ca2+. The addition of Ca2+ or Mg2+ to the bilayer system inhibited the peptide K+ carrier activity. Three possible explanations of this interesting Ca2+ inhibition of carrier activity are irreversible complexation of Ca2+, mixed ligand complex formation involving Ca2+, lipid and peptide, and impermeability of the lipid layer when peptide is complexed with a divalent cation. |
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