Exposure of helices 4 and 5 is required for insecticidal activity of Cry2Ab by promoting assembly of a prepore oligomeric structure
Exposure of helices 4 and 5 is required for insecticidal activity of Cry2Ab by promoting assembly of a prepore oligomeric structure
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通过促进前孔寡聚结构的组装，Cry2Ab 的杀虫活性需要暴露螺旋 4 和 5
DOI：
10.1111/cmi.12827
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发表时间：
2018
影响因子：
3.4
通讯作者：
Chen Qing-Xi
中科院分区：
文献类型：
--
作者：
Xu Lian;Pan Zhi-Zhen;Zhang Jing;Niu Li-Yang;Li Jie;Chen Zheng;Liu Bo;Zhu Yu-Jing;Chen Qing-Xi
Cry2Ab是一种从苏云金芽孢杆菌中提取的成孔毒素，在世界范围内被广泛用于防治鳞翅目害虫。先前的研究表明，小菜蛾菌液对Cry2Ab的蛋白水解激活是其对stp具有杀虫活性的必要条件。小菜，虽然确切的分子机制尚不清楚。在这里，我们首次证明了Cry2Ab的蛋白水解发现了一个活性区域（结构域I中的螺旋α4和α5），这是Cry2Ab的作用模式所必需的。α4和α5螺旋的掩蔽或去除均介导了Cry2Ab的杀虫活性。α4和α5螺旋的暴露不能促进Cry2Ab toP的结合。但确实诱导Cry2Ab单体聚集并组装250‐kDa的预孔低聚物。位点定向诱变实验产生了位点指向α4和α5螺旋的Cry2Ab突变体，生物实验表明，一些不能形成寡聚物的Cry2Ab突变体显著降低了它们对stp的毒性。蛾。综上所述，我们的数据突出了α4和α5螺旋在Cry2Ab的作用模式中的重要性，并可能导致对Cry2Ab杀虫活性的更详细的研究。
Cry2Ab, a pore‐forming toxin derived fromBacillus thuringiensis, is widely used as a bio‐insecticide to control lepidopteran pests around the world. A previous study revealed that proteolytic activation of Cry2Ab byPlutella xylostellamidgut juice was essential for its insecticidal activity againstP. xylostella, although the exact molecular mechanism remained unknown. Here, we demonstrated for the first time that proteolysis of Cry2Ab uncovered an active region (the helices α4 and α5 in Domain I), which was required for the mode of action of Cry2Ab. Either the masking or the removal of helices α4 and α5 mediated the pesticidal activity of Cry2Ab. The exposure of helices α4 and α5 did not facilitate the binding of Cry2Ab toP. xylostellamidgut receptors but did induce Cry2Ab monomer to aggregate and assemble a 250‐kDa prepore oligomer. Site‐directed mutagenesis assay was performed to generate Cry2Ab mutants site directed on the helices α4 and α5, and bioassays suggested that some Cry2Ab variants that could not form oligomers had significantly lowered their toxicities againstP. xylostella. Taken together, our data highlight the importance of helices α4 and α5 in the mode of action of Cry2Ab and could lead to more detailed studies on the insecticidal activity of Cry2Ab.