European Biophysics Journal

, Volume 30, Issue 2, pp 147–161

Dynamics and orientation of amphipathic peptides in solution and bound to membranes: a steady-state and time-resolved fluorescence study of staphylococcal δ-toxin and its synthetic analogues

  • Jean-Claude Talbot
  • Eric Thiaudière
  • Michel Vincent
  • Jacques Gallay
  • Odile Siffert
  • Jean Dufourcq
Article

DOI: 10.1007/s002490000118

Cite this article as:
Talbot, JC., Thiaudière, E., Vincent, M. et al. Eur Biophys J (2001) 30: 147. doi:10.1007/s002490000118

Abstract.

The environment of both the hydrophilic and hydrophobic sides of α-helical δ-toxin are probed by tryptophanyl (Trp) fluorescence, when self-association occurs in solution and on binding to membranes. The fluorescence parameters of staphylococcal δ-toxin (Trp15 on the polar side of the amphipathic helix) and synthetic analogues with single Trp at position 5 or 16 (on the apolar side) were studied. The time-resolved fluorescence decays of the peptides in solution show that the local environment of their single Trp is always heterogeneous. Although the self-association degree increases with concentration, as shown by fluorescence anisotropy decays, the lifetimes (and their statistical weight) of Trp16 do not change, contrary to what is observed for Trp15. The first step of self-association is then driven by hydrophobic interactions between apolar sides of α-helices, whilst further oligomerization involves their polar side (Trp15) via electrostatic interactions. This is supported by dissociation induced by salt. For all self-associated peptides, the polarity of the Trp microenvironment was not significantly modified upon binding to phospholipid vesicles, as indicated by the small shifts of the fluorescence emission spectra and lifetime values. However, the relative populations of the lifetime classes vary with bound-peptide density similar to the rates of their global motions in bilayers or smaller particles. Quenching experiments by water or lipid-soluble compounds show changes of the orientation of membrane-inserted peptides, from probably dimers lying flat at the interface at low peptide density, to oligomers spanning the membrane and inducing membrane fragmentation at high peptide density.

δ-Toxin Fluorescence quenching Time-resolved fluorescence anisotropy Mobility Self-association 

Copyright information

© Springer-Verlag 2000

Authors and Affiliations

  • Jean-Claude Talbot
    • 1
  • Eric Thiaudière
    • 1
  • Michel Vincent
    • 2
  • Jacques Gallay
    • 2
  • Odile Siffert
    • 3
  • Jean Dufourcq
    • 1
  1. 1.Centre de Recherche Paul Pascal, CNRS, Av. A. Schweitzer, 33600 Pessac, France
  2. 2.LURE, CNRS-CEA-MEN, Université de Paris Sud, 91405 Orsay, France
  3. 3.Unité de Chimie Organique, Institut Pasteur, 25 rue du Dr Roux, 75015 Paris, France
  4. 4.Present address: Unité de Résonance Magnétique des Systèmes Biologiques, Université de Bordeaux II, 146 rue Léo Saignat, 33076 Bordeaux Cedex, France

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