title: Synthetic amphiphilic peptide models for protein ion channels.
abstract: Ion channel proteins are important for the conduction of ions across biological membranes. Recent analyses of their sequences have suggested that they are composed of bundles of alpha-helices that associate to form ion-conducting channels. To gain insight into the mechanisms by which alpha-helices can aggregate and conduct ions, three model peptides containing only leucine and serine residues were synthesized and characterized. A 21-residue peptide, H2N-(Leu-Ser-Ser-Leu-Leu-Ser-Leu)3-CONH2, which was designed to be a membrane-spanning amphiphilic alpha-helix, formed well-defined ion channels with ion permeability and lifetime characteristics resembling the acetylcholine receptor. In contrast, a 14-residue version of this peptide, which was too short to span the phospolipid bilayer as an alpha-helix, failed to form discrete, stable channels. A third peptide, H2N-(Leu-Ser-Leu-Leu-Leu-Ser-Leu)3-CONH2, in which one serine per heptad repeat was replaced by leucine, produced proton-selective channels. Computer graphics and energy minimization were used to create molecular models that were consistent with the observed properties of the channels.
mesh_terms: D003196:Computer Graphics; D004553:Electric Conductivity; D007473:Ion Channels; D007930:Leucine; D008565:Membrane Proteins; D008956:Models, Chemical; D008958:Models, Molecular; D010455:Peptides / Q000138:chemical synthesis; D011522:Protons; D012694:Serine
chemical_list: D007473:Ion Channels; D008565:Membrane Proteins; D010455:Peptides; D011522:Protons; D012694:Serine; D007930:Leucine