Conformational studies of amphipathic alpha-helical peptides containing an amino acid with a long alkyl chain and their anchoring to lipid bilayer liposomes.
In order to investigate the conformation and orientation of lipid-bound peptides and proteins in the lipid bilayer, basic amphipathic alpha-helical peptides with a long alkyl chain, palmitoyl-(Leu-Ala-Arg-Leu)3-NHCH3 (P-4(3)) and Ac-Leu-Ala-Arg-Leu-Trp-Amy-Arg-Leu-Leu-Ala-Arg-Leu-NHCH3 (Amy-4(3), Amy; alpha-aminomyristic acid) were designed and synthesized. The conformational features and spectroscopic behavior in a buffer solution and in neutral and acidic liposomes were studied by CD, dye-leakage, and fluorescence measurements. The CD data indicated that P-4(3) took an alpha-helical structure in aqueous solution and in neutral and acidic liposomes. On the other hand, Amy-4(3) took a beta-structure in aqueous solution and an alpha-helical structure in neutral and acidic liposomes. The conformational change of Amy-4(3) was confirmed by fluorescence study on lipid titration of the peptide. The dye-leakage experiment showed that both peptides interacted with acidic liposomes to perturb them, but less effectively than Ac-(Leu-Ala-Arg-Leu)3-NHCH3 (4(3)) which has no long alkyl group. Based on these results, a discussion is made concerning the conformation and orientation of peptides in aqueous solution and in the lipid bilayer.
Kato
T
T
Laboratory of Biochemistry, Faculty of Sciences, Kyushu University, Fukuoka, Japan.
Lee
S
S
Ono
S
S
Agawa
Y
Y
Aoyagi
H
H
Ohno
M
M
Nishino
N
N
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry*; D002942:Circular Dichroism; D008051:Lipid Bilayers; D008081:Liposomes / Q000378:metabolism*; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence
D000596:Amino Acids; D008051:Lipid Bilayers; D008081:Liposomes; D010455:Peptides