Structural and Functional Insights into the C-terminal Fragment of Insecticidal Vip3A Toxin ofBacillus thuringiensis
Structural and Functional Insights into the C-terminal Fragment of Insecticidal Vip3A Toxin ofBacillus thuringiensis
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苏云金芽孢杆菌杀虫 Vip3A 毒素 C 末端片段的结构和功能见解
DOI：
10.3390/toxins12070438
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发表时间：
2020-07-01
期刊：
影响因子：
4.2
通讯作者：
Gao, Xiang
中科院分区：
文献类型：
--
作者：
Jiang, Kun;Zhang, Yan;Gao, Xiang
苏云金芽孢杆菌（Bacillus thuringiensis）分泌的营养期杀虫蛋白（vegetative insecticidal protein，Vips）具有与目前应用的杀虫晶体蛋白（Cry toxins）不同的杀虫特性，被认为是新一代杀虫毒素。Vip 3A毒素代表绝大多数Vip，已在转基因作物和生物杀虫剂中商业化使用。然而，由于缺乏Vip 3A的结构信息和在分子水平上对其杀虫机理的清楚了解，限制了其进一步的开发和更广泛的应用。在这里，我们提出了第一个晶体结构的C-末端片段的Vip 3A毒素（Vip 3Aa 11（200-789））。由于该杀虫蛋白家族的所有成员都是高度保守的，因此Vip 3A的结构为杀虫毒素的Vip 3A家族的一般结构域结构和蛋白质折叠提供了独特的见解。我们的结构分析揭示了一个四域组织，具有潜在的膜插入区，受体结合域，和两个潜在的聚糖结合域的Vip 3A。此外，细胞毒性测定和昆虫生物测定表明，纯化的Vip 3Aa毒素的C-末端片段单独没有杀虫活性。总之，这些发现为Vip 3A家族杀虫毒素的作用模式提供了见解，并将促进Vip 3A开发成为更有效的生物杀虫剂。
The vegetative insecticidal proteins (Vips) secreted byBacillus thuringiensisare regarded as the new generation of insecticidal toxins because they have different insecticidal properties compared with commonly applied insecticidal crystal proteins (Cry toxins). Vip3A toxin, representing the vast majority of Vips, has been used commercially in transgenic crops and bio-insecticides. However, the lack of both structural information on Vip3A and a clear understanding of its insecticidal mechanism at the molecular level limits its further development and broader application. Here we present the first crystal structure of the C-terminal fragment of Vip3A toxin (Vip3Aa11(200-789)). Since all members of this insecticidal protein family are highly conserved, the structure of Vip3A provides unique insight into the general domain architecture and protein fold of the Vip3A family of insecticidal toxins. Our structural analysis reveals a four-domain organization, featuring a potential membrane insertion region, a receptor binding domain, and two potential glycan binding domains of Vip3A. In addition, cytotoxicity assays and insect bioassays show that the purified C-terminal fragment of Vip3Aa toxin alone have no insecticidal activity. Taken together, these findings provide insights into the mode of action of the Vip3A family of insecticidal toxins and will boost the development of Vip3A into more efficient bio-insecticides.