title: Design of membrane-inserting peptides: spectroscopic characterization with and without lipid bilayers.
abstract: This paper reports the spectroscopic characterization of two de novo peptides. The first sequence, Ala peptide = H2N-Ala27-Tyr-Lys6-CONH2, gives circular dichroism (CD) and Fourier transform infrared (FTIR) spectra characteristic of beta structure in solution, binds to lipid bilayer vesicles poorly, and tends to precipitate in buffered 0.1 M salt solutions. In the second sequence, Leu peptide = H2N-Ala2-Leu3-Ala22-Tyr-Lys6-CONH2, three leucines are substituted for three alanine residues. This small sequence change results in CD spectra that are characteristic of helical structures, while the FTIR spectra give evidence for complex equilibria between multiple structures in solution. The Leu peptide does not precipitate in buffered salt solutions and binds to lipid bilayers. The polarized attenuated total reflectance infrared spectra provide evidence of a transmembrane orientation for the helical peptide in lipid bilayers. The collective spectroscopic results are summarized in a tentative model in which the Leu peptide exhibits multiple equilibria between extended unordered, helix, and coiled-coil structures in solution; when lipid vesicles are added, the peptide binds to the lipid surface and then inserts into the lipid in a transmembrane orientation. The slow kinetics exhibited by the peptide suggest multiple conformational changes during the lipid-peptide interactions. The design rationale for the peptides is included in an appendix.
authors.affiliation: Department of Biochemistry, University of Virginia School of Medicine, Charlottesville 22908, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Chung
authors.forename: T E
authors.initials: TE
authors.lastname: Thompson
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D007700:Kinetics; D008051:Lipid Bilayers / Q000378:metabolism*; D008081:Liposomes / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D013053:Spectrophotometry; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature
chemical_list: D008051:Lipid Bilayers; D008081:Liposomes; D008565:Membrane Proteins; D010455:Peptides; D010713:Phosphatidylcholines; C028694:1-palmitoyl-2-oleoylphosphatidylcholine