title: Interactions of a synthetic Leu-Lys-rich antimicrobial peptide with phospholipid bilayers.
abstract: The interaction of the synthetic antimicrobial peptide P5 (KWKKLLKKPLLKKLLKKL-NH(2)) with model phospholipid membranes was studied using solid-state NMR and circular dichroism (CD) spectroscopy. P5 peptide had little secondary structure in buffer, but addition of large unilamellar vesicles (LUV) composed of dimyristoylphosphatidylcholine (DMPC) increased the β-sheet content to ~20%. Addition of negatively charged LUV, DMPC-dimyristoylphosphatidylglycerol (DMPG) 2:1, led to a substantial (~40%) increase of the α-helical conformation. The peptide structure did not change significantly above and below the phospholipid phase transition temperature. P5 peptide interacted differently with DMPC bilayers with deuterated acyl chains (d(54)-DMPC) and mixed d(54)-DMPC-DMPG bilayers, used to mimic eukaryotic and prokaryotic membranes, respectively. In DMPC vesicles, P5 peptide had no significant interaction apart from slightly perturbing the upper region of the lipid acyl chain with minimum effect at the terminal methyl groups. By contrast, in the DMPC-DMPG vesicles the peptide increased disorder throughout the entire acyl chain of DMPC in the mixed bilayer. P5 promoted disordering of the headgroup of neutral membranes, observed by (31)P NMR. However, no perturbations in the T(1) relaxation nor the T(2-) values were observed at 30°C, although a slight change in the dynamics of the headgroup at 20°C was noticeable compared with peptide-free vesicles. However, the P5 peptide caused similar perturbations of the headgroup of negatively charged vesicles at both temperatures. These data correlate with the non-haemolytic activity of the P5 peptide against red blood cells (neutral membranes) while inhibiting bacterial growth (negatively charged membranes).
authors.affiliation: School of Chemistry, Bio21 Institute, University of Melbourne, Melbourne, VIC 3010, Australia.
authors.forename: David I
authors.initials: DI
authors.lastname: Fernandez
authors.forename: Marc-Antoine
authors.initials: MA
authors.lastname: Sani
authors.forename: John D
authors.initials: JD
authors.lastname: Gehman
authors.forename: Kyung-Soo
authors.initials: KS
authors.lastname: Hahm
authors.forename: Frances
authors.initials: F
authors.lastname: Separovic
mesh_terms: D000595:Amino Acid Sequence; D000890:Anti-Infective Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D023181:Antimicrobial Cationic Peptides / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D002942:Circular Dichroism / Q000379:methods; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry / Q000378:metabolism; D005057:Eukaryotic Cells / Q000737:chemistry / Q000378:metabolism; D007930:Leucine / Q000737:chemistry / Q000378:metabolism*; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism*; D008239:Lysine / Q000737:chemistry / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008969:Molecular Sequence Data; D010715:Phosphatidylglycerols / Q000737:chemistry / Q000378:metabolism; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism*; D010759:Phosphorus Isotopes; D011387:Prokaryotic Cells / Q000737:chemistry / Q000378:metabolism; D013696:Temperature
chemical_list: D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; D008051:Lipid Bilayers; D010715:Phosphatidylglycerols; D010743:Phospholipids; D010759:Phosphorus Isotopes; C002773:dimyristoylphosphatidylglycerol; D007930:Leucine; D008239:Lysine; D004134:Dimyristoylphosphatidylcholine