title: Structure of (KIAGKIA)3 aggregates in phospholipid bilayers by solid-state NMR.
abstract: The interchain (13)C-(19)F dipolar coupling measured in a rotational-echo double-resonance (REDOR) experiment performed on mixtures of differently labeled KIAGKIA-KIAGKIA-KIAGKIA (K3) peptides (one specifically (13)C labeled, and the other specifically (19)F labeled) in multilamellar vesicles of dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylglycerol (1:1) shows that K3 forms close-packed clusters, primarily dimers, in bilayers at a lipid/peptide molar ratio (L/P) of 20. Dipolar coupling to additional peptides is weaker than that within the dimers, consistent with aggregates of monomers and dimers. Analysis of the sideband dephasing rates indicates a preferred orientation between the peptide chains of the dimers. The combination of the distance and orientation information from REDOR is consistent with a parallel (N-N) dimer structure in which two K3 helices intersect at a cross-angle of approximately 20 degrees. Static (19)F NMR experiments performed on K3 in oriented lipid bilayers show that between L/P = 200 and L/P = 20, K3 chains change their absolute orientation with respect to the membrane normal. This result suggests that the K3 dimers detected by REDOR at L/P = 20 are not on the surface of the bilayer but are in a membrane pore.
authors.affiliation: Department of Chemistry, Washington University, St. Louis, Missouri 63130, USA.
authors.forename: Orsolya
authors.initials: O
authors.lastname: Toke
authors.forename: R D
authors.initials: RD
authors.lastname: O'Connor
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Weldeghiorghis
authors.forename: W Lee
authors.initials: WL
authors.lastname: Maloy
authors.forename: Ralf W
authors.initials: RW
authors.lastname: Glaser
authors.forename: Anne S
authors.initials: AS
authors.lastname: Ulrich
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*; D019281:Dimerization; 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*
chemical_list: D000900:Anti-Bacterial Agents; D008051:Lipid Bilayers; D010455:Peptides; D010743:Phospholipids; D015060:1,2-Dipalmitoylphosphatidylcholine