Solid-state NMR investigation of the selective perturbation of lipid bilayers by the cyclic antimicrobial peptide RTD-1.
RTD-1 is a cyclic beta-hairpin antimicrobial peptide isolated from rhesus macaque leukocytes. Using (31)P, (2)H, (13)C, and (15)N solid-state NMR, we investigated the interaction of RTD-1 with lipid bilayers of different compositions. (31)P and (2)H NMR of uniaxially oriented membranes provided valuable information about how RTD-1 affects the static and dynamic disorder of the bilayer. Toward phosphatidylcholine (PC) bilayers, RTD-1 causes moderate orientational disorder independent of the bilayer thickness, suggesting that RTD-1 binds to the surface of PC bilayers without perturbing its hydrophobic core. Addition of cholesterol to the POPC membrane does not affect the orientational disorder. In contrast, binding of RTD-1 to anionic bilayers containing PC and phosphatidylglycerol lipids induces much greater orientational disorder without affecting the dynamic disorder of the membrane. These correlate with the selectivity of RTD-1 for anionic bacterial membranes as opposed to cholesterol-rich zwitterionic mammalian membranes. Line shape simulations indicate that RTD-1 induces the formation of micrometer-diameter lipid cylinders in anionic membranes. The curvature stress induced by RTD-1 may underlie the antimicrobial activity of RTD-1. (13)C and (15)N anisotropic chemical shifts of RTD-1 in oriented PC bilayers indicate that the peptide adopts a distribution of orientations relative to the magnetic field. This is most likely due to a small fraction of lipid cylinders that change the RTD-1 orientation with respect to the magnetic field. Membrane-bound RTD-1 exhibits narrow line widths in magic-angle spinning spectra, but the sideband intensities indicate rigid-limit anisotropies. These suggest that RTD-1 has a well-defined secondary structure and is likely aggregated in the membrane. These structural and dynamical features of RTD-1 differ significantly from those of PG-1, a related beta-hairpin antimicrobial peptide.
Buffy
Jarrod J
JJ
Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA.
McCormick
Melissa J
MJ
Wi
Sungsool
S
Waring
Alan
A
Lehrer
Robert I
RI
Hong
Mei
M
D000595:Amino Acid Sequence; D000818:Animals; D000838:Anions / Q000737:chemistry; D023181:Antimicrobial Cationic Peptides / Q000138:chemical synthesis / Q000378:metabolism*; D002462:Cell Membrane / Q000737:chemistry / Q000382:microbiology; D002784:Cholesterol / Q000737:chemistry; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism*; D008253:Macaca mulatta; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008956:Models, Chemical; D008969:Molecular Sequence Data; D010456:Peptides, Cyclic / Q000138:chemical synthesis / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000737:chemistry; D010759:Phosphorus Isotopes / Q000737:chemistry; D010767:Phosphorylcholine / Q000737:chemistry; D023084:alpha-Defensins
D000838:Anions; D023181:Antimicrobial Cationic Peptides; C429483:DEFA1A3 protein, human; D008051:Lipid Bilayers; D010456:Peptides, Cyclic; D010713:Phosphatidylcholines; D010759:Phosphorus Isotopes; D023084:alpha-Defensins; D010767:Phosphorylcholine; C002448:1,2-linoleoylphosphatidylcholine; D002784:Cholesterol; C028694:1-palmitoyl-2-oleoylphosphatidylcholine; D004134:Dimyristoylphosphatidylcholine