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Title: The C-terminal domain of the Bacillus thuringiensis Cry4Ba mosquito-specific toxin serves as a potential membrane anchor
Authors: Anon Thammasittirong
Chompounoot Imtong
Wilaiwan Sriwimol
Somsri Sakdee
Chanan Angsuthanasombat
Kasetsart University, Kamphaeng Saen Campus
Faculty of Medicine, Prince of Songkia University
Mahidol University
Prince of Songkla University
Biophysics Institute for Research and Development (BIRD)
Keywords: Environmental Science
Issue Date: 1-Jan-2019
Citation: Toxins. Vol.11, No.2 (2019)
Abstract: © 2019 by the authors. Licensee MDPI, Basel, Switzerland. Although the C-terminal domain (DIII) of three-domain Cry insecticidal toxins from Bacillus thuringiensis has been implicated in various biological functions, its exact role still remains to be elucidated. Here, the 21-kDa isolated DIII fragment of the 65-kDa Cry4Ba mosquito-specific toxin was analyzed for its binding characteristics toward lipid-bilayer membranes. When the highly-purified Cry4Ba-DIII protein was structurally verified by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, it revealed the presence of a distinct β-sheet structure, corresponding to its structure embodied in the Cry4Ba crystal structure. Binding analysis via surface plasmon resonance (SPR) spectroscopy revealed that the 21-kDa Cry4Ba-DIII truncate displayed tight binding to immobilized liposome membranes in a two-step manner, exhibiting a dissociation rate constant (k d ) comparable to the 65-kDa full-length toxin. Also similar to the Cry4Ba full-length toxin, its isolated DIII truncate was able to anchor a part of its molecule into the immobilized membrane as the SPR signal was still detected after prolonged treatment with proteinase K. However, unlike the full-length active toxin, the DIII truncate was unable to induce membrane permeability of calcein-loaded liposomes or ion-channel formation in planar lipid bilayers. Together, our present data have disclosed a pivotal role of C-terminal DIII in serving as a membrane anchor rather than a pore-forming moiety of the Cry4Ba mosquito-active toxin, highlighting its potential mechanistic contribution to the interaction of the full-length toxin with lipid membranes in mediating toxicity.
ISSN: 20726651
Appears in Collections:Scopus 2019

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