Pan Zhi-Zhen, Xu Lian, Liu Bo, Chen Qing-Xi, Zhu Yu-Jing
Agricultural Bio-Resources Research Institute, Fujian Academy of Agricultural Sciences, Fuzhou, 350003, China.
School of Life Sciences, Xiamen University, Xiamen, 361005, China.
AMB Express. 2021 Jul 31;11(1):112. doi: 10.1186/s13568-021-01270-0.
As a pore-forming toxin, activation, oligomerization and pore-formation were both required for the mode of action of Cry toxins. Previous results revealed that the helices α4-α5 of Domain I were involved in the oligomerization of Cry2Ab, however, the key residues for Cry2Ab aggregation remained ambiguous. In present studies, we built 20 Cry2Ab alanine mutants site-directed in the helices α4-α5 of Domain I and demonstrated that mutants N151A, T152A, F157A, L183A, L185A and I188A could reduce the assembly of the 250 kDa oligomers, suggesting that these mutation residues might be essential for Cry2Ab oligomerization. As expected, all of these variants showed lower insecticidal activity against P. xylostella. Furthermore, we found that the pore-forming activities of these mutants also decreased when compared to wild-type Cry2Ab. Taken together, our data identified key residues for Cry2Ab oligomerization and emphasized that oligomerization was closely related to the insecticidal activity and pore-forming activity of Cry2Ab.
作为一种成孔毒素，激活、寡聚化和孔形成都是Cry毒素发挥作用方式所必需的。先前的结果表明，结构域I的α4-α5螺旋参与了Cry2Ab的寡聚化，然而，Cry2Ab聚集的关键残基仍不明确。在目前的研究中，我们构建了20个在结构域I的α4-α5螺旋中定点的Cry2Ab丙氨酸突变体，并证明突变体N151A、T152A、F157A、L183A、L185A和I188A可以减少250 kDa寡聚体的组装，这表明这些突变残基可能对Cry2Ab寡聚化至关重要。正如预期的那样，所有这些变体对小菜蛾的杀虫活性都较低。此外，我们发现与野生型Cry2Ab相比，这些突变体的成孔活性也降低了。综上所述，我们的数据确定了Cry2Ab寡聚化的关键残基，并强调寡聚化与Cry2Ab的杀虫活性和成孔活性密切相关。
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