Solid-State NMR Investigation of the Selective Perturbation of Lipid Bilayers by the Cyclic Antimicrobial Peptide RTD-1
- 8 July 2004
- journal article
- research article
- Published by American Chemical Society (ACS) in Biochemistry
- Vol. 43 (30), 9800-9812
- https://doi.org/10.1021/bi036243w
Abstract
RTD-1 is a cyclic β-hairpin antimicrobial peptide isolated from rhesus macaque leukocytes. Using 31P, 2H, 13C, and 15N solid-state NMR, we investigated the interaction of RTD-1 with lipid bilayers of different compositions. 31P and 2H 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. 13C and 15N 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 β-hairpin antimicrobial peptide.Keywords
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