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The Journal of Membrane Biology

, Volume 184, Issue 2, pp 171–183 | Cite as

Permeabilization of Model Lipid Membranes by Bacillus sphaericus Mosquitocidal Binary Toxin and its Individual Components

  • J.-L.  Schwartz
  • L.  Potvin
  • F.  Coux
  • J.-F.  Charles
  • C.  Berry
  • M.J.  Humphreys
  • A.F.  Jones
  • I.  Bernhart
  • M.  Dalla Serra
  • G.  Menestrina

Abstract.

The high larvicidal effect of Bacillus sphaericus (Bs), a mosquito control agent, originates from the presence of a binary toxin (Bs Bin) composed of two proteins (BinA and BinB) that work together to lyse gut cells of susceptible larvae. We demonstrate for the first time that the binary toxin and its individual components permeabilize receptor-free large unilamellar phospholipid vesicles (LUVs) and planar lipid bilayers (PLBs) by a mechanism of pore formation. Calcein-release experiments showed that LUV permeabilization was optimally achieved at alkaline pH and in the presence of acidic lipids. BinA was more efficient than BinB, BinB facilitated the BinA effect, and their stoichiometric mixture was more effective than the full Bin toxin. In PLBs, BinA formed voltage-dependent channels of ≈100–200 pS with long open times and a high open probability. Larger channels (≥400 pS) were also observed. BinB, which inserted less easily, formed smaller channels (≤100 pS) with shorter mean open times. Channels observed after sequential addition of the two components, or formed by their 1:1 mixture (w/w), displayed BinA-like activity. Bs Bin toxin was less efficient at forming channels than the BinA/BinB mixture, with channels displaying the BinA channel behavior. Our data support the concept of BinA being principally responsible for pore formation in lipid membranes with BinB, the binding component of the toxin, playing a role in promoting channel activity.

Key words:Bacillus sphaericus— Pore-forming toxin — Planar lipid bilayers — Lipid vesicles — Calcein release — Ion channels 

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Copyright information

© Springer-Verlag New York Inc. 2001

Authors and Affiliations

  • J.-L.  Schwartz
    • 1
  • L.  Potvin
    • 1
  • F.  Coux
    • 2
  • J.-F.  Charles
    • 3
  • C.  Berry
    • 4
  • M.J.  Humphreys
    • 4
  • A.F.  Jones
    • 4
  • I.  Bernhart
    • 5
  • M.  Dalla Serra
    • 5
  • G.  Menestrina
    • 5
  1. 1.Biotechnology Research Institute, Montreal, Quebec, Canada, H4P 2R2CA
  2. 2.Groupe de Recherche en Transport Membranaire, Université de Montréal, C.P. 6128, Succ. Centre-Ville Montreal, Quebec, Canada, H3C 3J7CA
  3. 3.Institut Pasteur, Bactéries Entomopathogènes, 75724 Paris, FranceFR
  4. 4.Cardiff School of Biosciences, Cardiff University, P.O. Box 911, Museum Avenue, Cardiff, CF10 3US, UKGB
  5. 5.CNR-ITC, Centro di Fisica degli Stati Aggregati, Via Sommarive 18, I-38050 Povo, ItalyIT

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