Luo K, Banks D, Adang M J
Department of Entomology, University of Georgia, Athens, Georgia 30602, USA.
Appl Environ Microbiol. 1999 Feb;65(2):457-64. doi: 10.1128/AEM.65.2.457-464.1999.
The binding and pore formation properties of four Bacillus thuringiensis Cry1 toxins were analyzed by using brush border membrane vesicles from Spodoptera exigua and Spodoptera frugiperda, and the results were compared to the results of toxicity bioassays. Cry1Fa was highly toxic and Cry1Ac was nontoxic to S. exigua and S. frugiperda larvae, while Cry1Ca was highly toxic to S. exigua and weakly toxic to S. frugiperda. In contrast, Cry1Bb was active against S. frugiperda but only marginally active against S. exigua. Bioassays performed with iodinated Cry1Bb, Cry1Fa, and Cry1Ca showed that the effects of iodination on toxin activity were different. The toxicities of I-labeled Cry1Bb and Cry1Fa against Spodoptera species were significantly less than the toxicities of the unlabeled toxins, while Cry1Ca retained its insecticidal activity when it was labeled with 125I. Binding assays showed that iodination prevented Cry1Fa from binding to Spodoptera brush border membrane vesicles. 125I-labeled Cry1Ac, Cry1Bb, and Cry1Ca bound with high-affinities to brush border membrane vesicles from S. exigua and S. frugiperda. Competition binding experiments performed with heterologous toxins revealed two major binding sites. Cry1Ac and Cry1Fa have a common binding site, and Cry1Bb, Cry1C, and Cry1Fa have a second common binding site. No obvious relationship between dissociation of bound toxins from brush border membrane vesicles and toxicity was detected. Cry1 toxins were also tested for the ability to alter the permeability of membrane vesicles, as measured by a light scattering assay. Cry1 proteins toxic to Spodoptera larvae permeabilized brush border membrane vesicles, but the extent of permeabilization did not necessarily correlate with in vivo toxicity.
利用甜菜夜蛾和草地贪夜蛾的刷状缘膜囊泡分析了四种苏云金芽孢杆菌Cry1毒素的结合和孔形成特性，并将结果与毒性生物测定结果进行了比较。Cry1Fa对甜菜夜蛾和草地贪夜蛾幼虫具有高毒性，而Cry1Ac对它们无毒，Cry1Ca对甜菜夜蛾具有高毒性，对草地贪夜蛾毒性较弱。相比之下，Cry1Bb对草地贪夜蛾有活性，但对甜菜夜蛾只有微弱活性。用碘化的Cry1Bb、Cry1Fa和Cry1Ca进行的生物测定表明，碘化对毒素活性的影响不同。I标记的Cry1Bb和Cry1Fa对夜蛾科昆虫的毒性明显低于未标记毒素的毒性，而Cry1Ca用125I标记时仍保留其杀虫活性。结合试验表明，碘化阻止了Cry1Fa与夜蛾科刷状缘膜囊泡的结合。125I标记的Cry1Ac、Cry1Bb和Cry1Ca与甜菜夜蛾和草地贪夜蛾的刷状缘膜囊泡具有高亲和力结合。用异源毒素进行的竞争结合实验揭示了两个主要结合位点。Cry1Ac和Cry1Fa有一个共同的结合位点，Cry1Bb、Cry1C和Cry1Fa有第二个共同的结合位点。未检测到结合毒素从刷状缘膜囊泡解离与毒性之间的明显关系。还通过光散射测定法测试了Cry1毒素改变膜囊泡通透性的能力。对夜蛾科幼虫有毒的Cry1蛋白使刷状缘膜囊泡通透性增加，但通透性的程度不一定与体内毒性相关。
