Publication: The C-terminal domain of the Bacillus thuringiensis Cry4Ba mosquito-specific toxin serves as a potential membrane anchor
Issued Date
2019-01-01
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ISSN
20726651
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2-s2.0-85060544183
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Mahidol University
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SCOPUS
Bibliographic Citation
Toxins. Vol.11, No.2 (2019)
Suggested Citation
Anon Thammasittirong, Chompounoot Imtong, Wilaiwan Sriwimol, Somsri Sakdee, Chanan Angsuthanasombat The C-terminal domain of the Bacillus thuringiensis Cry4Ba mosquito-specific toxin serves as a potential membrane anchor. Toxins. Vol.11, No.2 (2019). doi:10.3390/toxins11020062 Retrieved from: https://repository.li.mahidol.ac.th/handle/20.500.14594/50941
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Title
The C-terminal domain of the Bacillus thuringiensis Cry4Ba mosquito-specific toxin serves as a potential membrane anchor
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.
