title: Secondary structure and lipid contact of a peptide antibiotic in phospholipid bilayers by REDOR.
abstract: The chemical shifts of specific (13)C and (15)N labels distributed throughout KIAGKIA-KIAGKIA-KIAGKIA (K3), an amphiphilic 21-residue antimicrobial peptide, prove that the peptide is in an all alpha-helical conformation in the bilayers of multilamellar vesicles (MLVs) containing dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylglycerol (1:1). Rotational-echo double-resonance (REDOR) (13)C[(31)P] and (15)N[(31)P] experiments on the same labeled MLVs show that on partitioning into the bilayer, the peptide chains remain in contact with lipid headgroups. The amphipathic lysine side chains of K3 in particular appear to play a key role in the electrostatic interactions with the acidic lipid headgroups. In addition to the extensive peptide-headgroup contact, (13)C[(19)F] REDOR experiments on MLVs containing specifically (19)F-labeled lipid tails suggest that a portion of the peptide is surrounded by a large number of lipid acyl chains. Complementary (31)P[(19)F] REDOR experiments on these MLVs show an enhanced headgroup-lipid tail contact resulting from the presence of K3. Despite these distortions, static (31)P NMR lineshapes indicate that the lamellar structure of the membrane is preserved.
authors.affiliation: Department of Chemistry, Washington University, St. Louis, Missouri 63130, USA.
authors.forename: Orsolya
authors.initials: O
authors.lastname: Toke
authors.forename: W Lee
authors.initials: WL
authors.lastname: Maloy
authors.forename: Sung Joon
authors.initials: SJ
authors.lastname: Kim
authors.forename: Jack
authors.initials: J
authors.lastname: Blazyk
authors.forename: Jacob
authors.initials: J
authors.lastname: Schaefer
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000737:chemistry*; D007553:Isotope Labeling; D008051:Lipid Bilayers / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D010455:Peptides; D010743:Phospholipids / Q000737:chemistry*; D017433:Protein Structure, Secondary
chemical_list: D000900:Anti-Bacterial Agents; D008051:Lipid Bilayers; D010455:Peptides; D010743:Phospholipids; D015060:1,2-Dipalmitoylphosphatidylcholine