title: Roles of peptide-peptide charge interaction and lipid phase separation in helix-helix association in lipid bilayer.
abstract: The roles of peptide-peptide charged interaction and lipid phase separation in helix-helix association in lipid bilayers were investigated using a model peptide, P(24), as a transmembrane alpha-helical peptide, and its four analogues. Fluorescence amino acids, tryptophan (P(24)W) and pyrenylalanine (P(24)Pya), were introduced into the sequence of P(24), respectively. Association of these peptides permits the resonance excitation energy transfer between tryptophan in P(24)W and pyrenylalanine in P(24)Pya or excimer formation between P(24)Pya themselves. To evaluate the effect of charged interaction on the association between alpha-helical transmembrane segments in membrane proteins, charged amino acids, glutamic acid (P(24)EW) and lysine (P(24)KPya), were introduced into P(24)W and P(24)Pya, respectively. Energy transfer experiments indicated that the charged interaction between the positive charge of lysine residue in P(24)KPya and the negative charge of glutamic acid residue in P(24)EW did not affect the aggregation of transmembrane peptides in lipid membranes. As the content ratio of sphingomyelin (SM) and cholesterol (Ch) was increased in the egg phosphatidylcholine (PC), the stronger excimer fluorescence spectra of P(24)Pya were observed, indicating that the co-existence of SM and Ch in PC liposomes, that is, the raft of SM and Ch, promotes the aggregation of the alpha-helical transmembrane peptides in lipid bilayers. Since the increase in the contents of SM and Ch leads to the decrease in the content of liquid crystalline-order phase, the moving area of transmembrane peptides might be limited in the liposomes, resulting in easy formation of the excimer in the presence of the lipid-raft.
authors.affiliation: Department of Chemistry, Faculty of Science, Fukuoka University, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Shigematsu
authors.forename: Minenosuke
authors.initials: M
authors.lastname: Matsutani
authors.forename: Tomomi
authors.initials: T
authors.lastname: Furuya
authors.forename: Taira
authors.initials: T
authors.lastname: Kiyota
authors.forename: Sannamu
authors.initials: S
authors.lastname: Lee
authors.forename: Gohsuke
authors.initials: G
authors.lastname: Sugihara
authors.forename: Shoji
authors.initials: S
authors.lastname: Yamashita
mesh_terms: D000595:Amino Acid Sequence; D002784:Cholesterol / Q000737:chemistry; D002942:Circular Dichroism; D015195:Drug Design; D004563:Electrochemistry; D004735:Energy Transfer; D066298:In Vitro Techniques; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry; D008854:Microscopy, Electron; D008958:Models, Molecular; D009842:Oligopeptides / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry; D011485:Protein Binding; D017368:Protein Prenylation; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence; D013109:Sphingomyelins / Q000737:chemistry; D014364:Tryptophan / Q000737:chemistry
chemical_list: D008051:Lipid Bilayers; D008081:Liposomes; D009842:Oligopeptides; D010713:Phosphatidylcholines; D013109:Sphingomyelins; D014364:Tryptophan; D002784:Cholesterol