Structural studies of Bacillus thuringiensis Cry Toxins

描述(申请人提供)：苏云金芽孢杆菌Cry蛋白是一种新型细菌毒素，实际应用于针对特定作物害虫(毛虫、甲虫、线虫)和病媒(蚊子)的生物杀虫剂。昆虫摄取苏云金芽孢杆菌晶体[或孢子和晶体]会导致Cry蛋白的溶解和蛋白分解处理，这些蛋白被认为是寡聚的，然后插入昆虫的中肠细胞。在主要的作用机制模型中，这种插入导致阳离子特异性离子通道的形成，使中肠细胞的电化学梯度崩溃，最终导致昆虫死亡。了解Cry蛋白如何插入细胞膜的一个重要步骤是了解Cry蛋白结构的可溶性和膜插入形式。结晶学的努力已经提供了几种Cry蛋白变体的可溶性结构，但到目前为止还没有确定Cry蛋白的膜插入形式的结构。这项R21拨款将探索确定这种膜插入Cry毒素的结构的策略。公共卫生相关性：苏云金芽孢杆菌Cry蛋白是一种新型细菌毒素，具有实际应用价值，可作为生物杀虫剂用于特定靶标的农作物害虫和病媒。这项提议寻求确定Cry毒素以杀死昆虫的形式的结构，这一知识可以用来产生改进的毒素。这种超级哭泣毒素可以通过增加作物产量来改善人类健康，从而帮助减少人类营养不良，并通过杀死可以传播疾病的蚊子来降低发病率。

DESCRIPTION (provided by applicant): The Bacillus thuringiensis Cry proteins are novel bacterial toxins with practical application as biological insecticides for the targeting of specific crop pests (caterpillars, beetles, nematodes) and disease vectors (mosquitoes). Insect ingestion of B. thuringiensis crystals [or spores and crystals] leads to solublization and proteolytic processing of Cry proteins that are thought to oligomerize and then insert into the midgut cells of insect. In the leading model for mechanism of action, this insertion results in the formation of cation-specific ion channels that collapse the electrochemical gradient of the midgut cells and ultimately leads to insect death. One important step towards understanding how Cry proteins insert into membranes would be the availability of Cry protein structures in both their soluble and membrane-inserted forms. Crystallographic efforts have provided structures of several Cry protein variants in their soluble forms, but as yet no structure of a Cry protein in its membrane inserted-form has been determined. This R21 grant will explore strategies towards the structural determination of such a membrane-inserted Cry toxin. PUBLIC HEALTH RELEVANCE: The Bacillus thuringiensis Cry proteins are novel bacterial toxins with practical application as biological insecticides for the specific targeting of insect crop pests and disease vectors. This proposal seeks to determine the structure of Cry toxins in the form that kills insects, knowledge that could be used to generate improved toxins. Such super Cry toxins could be used to improve human health by increasing crop yields, thereby helping to reduce human malnutrition, and by killing mosquitoes that can transmit diseases, resulting in lower incidence of sickness.