STRUCTURAL STUDY OF HEAT-LABILE ENTEROTOXIN

该项目包括大肠杆菌热- 不稳定肠毒素（LT）。LT是一类细菌的成员， 肠毒素是直接导致各种疾病的原因 严重性。与霍乱弧菌（Vibrio cholesterol）密切相关的肠毒素 毒素）产生一种可能导致死亡的严重的霍乱病 在数小时内; LT本身产生的轻度感染性腹泻， 在发达国家很少危及生命，但却是 第三世界的婴儿死亡率全球每年的发病率为 估计高达6.5亿箱，产量高达80万箱 每年死亡。 这项建议的具体目的包括阐明约束力的方式， 与细胞膜受体结合， 在感染细胞中的靶蛋白的识别，以及在感染细胞中的催化蛋白的识别。 酶活性A亚基的机制。这些结构 通过高分辨率X射线衍射蛋白质， 天然的和工程化的结构测定和分析 与模型寡糖和底物复合的LT变体 类似物 该项目的长期目标是： (l)指导设计有效的药物和疫苗， 通过提供结构上的解释， 这些蛋白质的生物学功能和活性。LT和霍乱毒素 在序列上80%同源，表现出类似的亚基机制， 组装，是免疫学上 交叉反应，结合G-M1神经节苷脂作为膜受体，并共享 在掺入细胞后的共同作用机制。因此 预计LT的研究也与霍乱直接相关。 (2)利用LT的显著能力刺激粘膜 通过设计原型疫苗的基础上纳入免疫系统 外源抗原决定簇进入LT结构。建议的设计包括 引入源自流感病毒血凝素的表位， 引入源自疟疾寄生虫疟原虫的表位 恶性疟原虫。

This project encompasses the structural study of Escherichia coli heat- labile enterotoxin (LT). LT is a member of a class of bacterial enterotoxins which are directly responsible for diseases of varying severity. The closely related enterotoxin from Vibrio cholerae (cholera toxin) produces a severe diarrheal disease which may result in death within hours; the milder infectious diarrhea produced by LT itself is rarely life-threatening in the developed world, but is a major cause of infant death in the third world. The annual incidence worldwide is estimated to be as high as 650 million cases, producing up to 800,000 deaths annually. Specific aims of this proposal include elucidation of the mode of binding to the cell membrane receptor, of the determinants for specific recognition of target proteins in the infected cell, and of the catalytic mechanism of the enzymatically active A subunit. These structural questions are to be explored via high resolution x-ray diffraction protein structure determination and analysis of both native and engineered variants of LT complexed with model oligosaccharides and substrate analogues. Long-term goals of this project are: (l) to guide design of drugs and vaccines effective against enterotoxigenic diseases by providing a structural explanation for the biological function and activity of these proteins. LT and cholera toxin are 80% homologous in sequence, exhibit similar mechanisms of subunit assembly, are immunologically cross-reactive, bind to G-M1 gangliosides as membrane receptors, and share a common mechanism of action after incorporation into the cell. Therefore studies on LT are expected to be directly relevant to cholera as well. (2) to utilize the remarkable ability of LT to stimulate the mucosal immune system by designing prototype vaccines based on the incorporation of foreign epitopes into the LT structure. Proposed designs include incorporation of epitopes derived from influenza virus hemagglutinin and incorporation of epitopes derived from the malarial parasite Plasmodium falciparum.