title: Interaction of mastoparan with membranes studied by 1H-NMR spectroscopy in detergent micelles and by solid-state 2H-NMR and 15N-NMR spectroscopy in oriented lipid bilayers.
abstract: Several complementary NMR approaches were used to study the interaction of mastoparan, a 14-residue peptide toxin from wasp venom, with lipid membranes. First, the 3D structure of mastoparan was determined using 1H-NMR spectroscopy in perdeuterated (SDS-d25) micelles. NOESY experiments and distance geometry calculations yielded a straight amphiphilic alpha-helix with high-order parameters, and the chemical shifts of the amide protons showed a characteristic periodicity of 3-4 residues. Secondly, solid-state 2H-NMR spectoscopy was used to describe the binding of mastoparan to lipid bilayers, composed of headgroup-deuterated dimyristoylglycerophosphocholine (DMPC-d4) and dimyristoylphosphatidylglycerol (DMPG). By correlating the deuterium quadrupole splittings of the alpha-segments and beta-segments, it was possible to differentiate the electrostatically induced structural response of the choline headgroup from dynamic effects induced by the peptide. A partial phase separation was observed, leading to a DMPG-rich phase and a DMPG-depleted phase, each containing some mastoparan. Finally, the insertion and orientation of a specifically 15N-labeled mastoparan (at position Ala10) in the bilayer environment was investigated by solid-state 15N-NMR spectroscopy, using macroscopically oriented samples. Two distinct orientational states were observed for the mastoparan helix, namely an in-plane and a trans-membrane alignment. The two populations of 90% in-plane and 10% trans-membrane helices are characterized by a mosaic spread of +/- 30 degrees and +/- 10 degrees, respectively. The biological activity of mastoparan is discussed in terms of a pore-forming model, as the peptide is known to be able to induce nonlamellar phases and facilitate a flip-flop between the monolayers.
authors.affiliation: Department of Biotechnology, Tokyo University of Agriculture and Technology, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Hori
authors.forename: M
authors.initials: M
authors.lastname: Demura
authors.forename: M
authors.initials: M
authors.lastname: Iwadate
authors.forename: A S
authors.initials: AS
authors.lastname: Ulrich
authors.forename: T
authors.initials: T
authors.lastname: Niidome
authors.forename: H
authors.initials: H
authors.lastname: Aoyagi
authors.forename: T
authors.initials: T
authors.lastname: Asakura
mesh_terms: D003903:Deuterium; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D036341:Intercellular Signaling Peptides and Proteins; D008051:Lipid Bilayers / Q000737:chemistry*; D008823:Micelles; D009587:Nitrogen Isotopes; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides; D010715:Phosphatidylglycerols / Q000737:chemistry; D011487:Protein Conformation; D011522:Protons; D014862:Wasp Venoms / Q000737:chemistry*
chemical_list: D036341:Intercellular Signaling Peptides and Proteins; D008051:Lipid Bilayers; D008823:Micelles; D009587:Nitrogen Isotopes; D010455:Peptides; D010715:Phosphatidylglycerols; D011522:Protons; D014862:Wasp Venoms; C037500:mastoparan; D003903:Deuterium; C002773:dimyristoylphosphatidylglycerol; D004134:Dimyristoylphosphatidylcholine