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Lipid-induced Pore Formation of the Bacillus thuringiensis Cry1Aa Insecticidal Toxin |
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| Authors: | V. Vié N. Van Mau P. Pomarède C. Dance J.L. Schwartz R. Laprade R. Frutos C. Rang L. Masson F. Heitz C. Le Grimellec |
| Affiliation: | (1) CBS, 29 rue de Navacelles, 34090 Montpellier Cedex, France, FR;(2) CRBM, CNRS-UPR 1086, 1919 route de Mende, 34293 Montpellier Cedex 5, France, FR;(3) CIRAD, Avenue Agropolis, BP 5035, 34032 Montpellier Cedex 1, France, FR;(4) Groupe de Recherche en Transport Membranaire, Université de Montréal, Montréal, Quebec H3C 2J7, Canada, CA;(5) Biotechnology Research Institute, 6100 Royalmount Avenue, Montréal, Quebec H4P 2R2, Canada, CA |
| Abstract: | After activation, Bacillus thuringiensis (Bt) insecticidal toxin forms pores in larval midgut epithelial cell membranes, leading to host death. Although the crystal structure of the soluble form of Cry1Aa has been determined, the conformation of the pores and the mechanism of toxin interaction with and insertion into membranes are still not clear. Here we show that Cry1Aa spontaneously inserts into lipid mono- and bilayer membranes of appropriate compositions. Fourier Transform InfraRed spectroscopy (FTIR) indicates that insertion is accompanied by conformational changes characterized mainly by an unfolding of the β-sheet domains. Moreover, Atomic Force Microscopy (AFM) imaging strongly suggests that the pores are composed of four subunits surrounding a 1.5 nm diameter central depression. Received: 14 July 2000/Revised: 28 December 2000 |
| Keywords: | : Lipid monolayers — Protein insertion — Cry1Aa toxin — Amphipathic properties — Pore formation |
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