SHIGELLA TOXIN: STRUCTURE & FUNCTION RELATIONSHIPS

志贺氏菌病是一种世界性的疾病， 而在发展中国家， mortality. 发病机制涉及结肠上皮的侵袭 细胞 蛋白质毒素现在被认为是第二个重要的 毒力因子 相同或非常相似的毒素是由 非侵袭性肠致病性E.大肠杆菌和其他生物。 的 毒素分子由1条A链和5条B链组成。 一 B链的功能作用是介导毒素与 真核细胞表面。 糖脂被证明是一种毒素 受体和具有不同糖的糖蛋白受体 特异性（GlcNAc 3）也涉及。 本方案旨在研究基本结构-功能 毒素B链的关系。 将特别强调 置于两个结合结构域的结构位置上， 它们在介导生物活动中的生物学作用， 毒素 通过使用糖蛋白受体类似物， 壳四糖，这两个结合域的直接证据将 首先要记录。 由于B链以多聚体形式存在， 单个单体和/或B与B相互作用的区域。 一 将使用化学交联剂来确定 结合域的链位置。 通过腔内注射 毒素与可溶性受体类似物的作用 将分析介导兔体液分泌的受体。 用来源于抗真菌药物的合成肽免疫兔 B链氨基酸序列将导致抗体， 测试了它们中和生物活性的能力， 毒素 这项研究的信息将对未来有用 设计安全有效的毒素疫苗。 最后，双方 B链的特定化学修饰，并通过研究 B链突变体氨基酸位置信息 将确定参与重要B链功能的。

Shigellosis is a world wide disease producing significant morbidity and in developing countries, a leading cause of diarrheal disease mortality. Pathogenesis involves invasion of colonic epithelial cells. A protein toxin is now believed to be a second improtant virulence factor. The same or very similar toxin is produced by non-invasive enteropathogenic E. coli and other organisms. The toxin molecule consists of one A chain and 5 B chains. A functional role of the B chains is to mediate toxin binding to the eukaryotic cell surface. A glycolipid has been shown to be a toxin receptor and a glycoprotein receptor with a different sugar specificity (GlcNAc3) is also involved. This proposal is designed to study basic structure-function relationships of the toxin B chain. Particular emphasis will be placed on the structrual location of the two binding domains and on their biological roles in mediating the biological activities of the toxin. Thorugh the use of the glycoprotein receptor analogue, chitotetraose, direct evidence for the two binding domains will first be documented. Since the B chains exist in multimer form in the individual monomers and/or regions of B to B interaction. A chemical cross-linker will be used to determine the inter or intra- chain location of the binding domains. By intraluminal injections of toxin with soluble receptor analogues the role of the two receptors in mediating fluid secretion in rabbits wil be analyzed. Immunization of rabbits with synthetic peptides derived from the B chain amino acid sequence will lead to antibodies that will be tested for their ability to neutralized the biological activity of toxin. Information from this study will be useful for the future design of safe and effective toxin vaccines. Finally by both specific chemical modification of the B chain and by the study of B chain mutants information on the location of amino acids involved in important B chain functions will be determined.