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Open AccessArticle

Cholesterol Increases Lipid Binding Rate and Changes Binding Behavior of Bacillus thuringiensis Cytolytic Protein

1
Institute for Biophysics, Department of Nanobiotechnology, University of Natural Resources and Life Sciences (BOKU), 1190 Vienna, Austria
2
National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), Pathumthani 12120, Thailand
*
Authors to whom correspondence should be addressed.
Current address: Institute of Pathophysiology and Allergy Research, Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, 1190 Vienna, Austria.
Int. J. Mol. Sci. 2018, 19(12), 3819; https://doi.org/10.3390/ijms19123819
Received: 16 October 2018 / Revised: 20 November 2018 / Accepted: 28 November 2018 / Published: 30 November 2018
(This article belongs to the Special Issue Atomic Force Microscopy for Biological Applications)
Cytolytic protein (Cyt) is a member of insecticidal proteins produced by Bacillus thuringiensis. Cyt protein has activity against insect cells and mammalian cells, which differ in lipid and cholesterol composition. This study presents the lipid binding behavior of Cyt2Aa2 protein on model membranes containing different levels of cholesterol content by combining Quartz Crystal Microbalance with Dissipation (QCM-D) and Atomic Force Microscopy (AFM). QCM-D results revealed that cholesterol enhances the binding rate of Cyt2Aa2 protein onto lipid bilayers. In addition, the thicker lipid bilayer was observed for the highest cholesterol content. These results were confirmed by AFM. The analysis of protein surface coverage as a function of time showed a slower process for 5:0 and 5:0.2 (POPC:Chol) ratios than for 5:1 and 5:2 (POPC:Chol) ratios. Significantly, the Cyt2Aa2-lipid binding behavior and the protein–lipid layer were different for the 5:3 (POPC:Chol) ratio. Furthermore, AFM images revealed a transformation of Cyt2Aa2/lipid layer structure from strip pattern to ring shape structures (which showed a strong repulsion with AFM tip). In summary, cholesterol increases the binding rate and alters the lipid binding behavior of Cyt2Aa2 protein, although it is not required for Cyt2Aa2 protein binding onto lipid bilayers. View Full-Text
Keywords: Bacillus thuringiensis; Cyt2Aa2 protein; cholesterol; QCM-D; AFM; lipid binding Bacillus thuringiensis; Cyt2Aa2 protein; cholesterol; QCM-D; AFM; lipid binding
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MDPI and ACS Style

Tharad, S.; Üzülmez, Ö.; Promdonkoy, B.; Toca-Herrera, J.L. Cholesterol Increases Lipid Binding Rate and Changes Binding Behavior of Bacillus thuringiensis Cytolytic Protein. Int. J. Mol. Sci. 2018, 19, 3819.

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