PG and Research Department of Zoology and Biotechnology, Lady Doak College, Madurai-625 002, TamilNadu, India.
J Biomol Struct Dyn. 2010 Dec;28(3):363-78. doi: 10.1080/07391102.2010.10507366.
A three dimensional model was developed for Cry10Aa protein sequence of B. thuringiensis LDC-9 and B. thuringiensis israelensis that has not been solved empirically by X-ray crystallography or NMR. Homology modeling was employed for the structure prediction using Cry2Aa as template protein, a high-resolution X-ray crystallography structure. The model predicted for the B. thuringiensis LDC-9 Cry10Aa protein reveals a partial N-terminal domain only due to its partial sequence of 104 amino acids. B. thuringiensis israelensis Cry10Aa model contains three domains such as domain I, a bundle of eight alpha helices with the central relatively hydrophobic helix surrounded by amphipathic helices while domain II and III contain mostly beta-sheets. Significant structural differences within domain II in this model among all Cry protein structures indicates that it is involved in recognition and binding to cell surfaces. Comparison of B. thuringiensis israelensis predicted structure with available experimentally determined Cry structures reveals identical folds. The distribution of electrostatic potential on the surface of the molecules in the model is non-uniform and identifies one side of the alpha-helical domain as negatively charged indicating orientation of toxic molecules toward the cell membrane during the initial binding with a cell surface receptor. The collective knowledge of Cry toxin structures will lead to a more critical understanding of the structural basis for receptor binding and pore formation, as well as allowing the scope of diversity to be better appreciated. This model will serve as a starting point for the design of mutagenesis experiments aimed to improve the toxicity and to provide a new tool for the elucidation of the mechanism of action of these mosquitocidal proteins.
为 B. thuringiensis LDC-9 和 B. thuringiensis israelensis 的 Cry10Aa 蛋白质序列开发了一个三维模型，该模型尚未通过 X 射线晶体学或 NMR 经验解决。使用 Cry2Aa 作为模板蛋白，采用同源建模进行结构预测，该蛋白具有高分辨率的 X 射线晶体结构。预测的 B. thuringiensis LDC-9 Cry10Aa 蛋白模型仅显示部分 N 端结构，因为其部分序列为 104 个氨基酸。B. thuringiensis israelensis Cry10Aa 模型包含三个结构域，如 I 结构域，由八个α螺旋组成的束，中央相对疏水区由两亲性螺旋包围，而 II 结构域和 III 结构域主要包含β片层。该模型中 II 结构域内所有 Cry 蛋白结构之间的结构差异表明其参与了与细胞表面的识别和结合。与可用的实验确定的 Cry 结构进行比较，B. thuringiensis israelensis 预测的结构显示出相同的折叠。模型中分子表面的静电势分布不均匀，并确定α螺旋结构域的一侧带负电荷，表明在与细胞膜初始结合过程中，毒分子的取向朝向细胞膜。Cry 毒素结构的综合知识将导致对受体结合和孔形成的结构基础有更深入的理解，并允许更好地理解多样性的范围。该模型将作为旨在提高毒性的诱变实验的起点，并为阐明这些杀蚊蛋白的作用机制提供新工具。
