SHIGELLA TOXIN: STRUCTURE & FUNCTION RELATIONSHIPS

志贺氏菌病是一种世界性疾病，发病率很高。 在发展中国家，腹泻病的一个主要原因 死亡率。发病机制与结肠上皮侵袭有关 细胞。一种蛋白质毒素现在被认为是第二种重要的 毒力因子。相同或非常相似的毒素是由 非侵袭性致病性大肠杆菌和其他生物。这个 毒素分子由1条A链和5条B链组成。一个 B链的功能作用是介导毒素与 真核细胞表面。糖脂已被证明是一种毒素 受体和糖蛋白受体具有不同的糖 特异性(GlcNAc3)也参与其中。 本方案旨在研究基本结构--功能 毒素B链的相互关系。特别强调的是 放置在两个结合域的结构位置上，以及 论它们在调节细菌生物活性中的生物学作用 毒素。通过使用糖蛋白受体类似物， 甲壳四糖，两个结合域的直接证据将 首先被记录在案。由于B链以多聚体形式存在于 B到B相互作用的单个单体和/或区域。一个 将使用化学交联剂来确定分子间或分子内 结合结构域的链位置。通过腔内注射 毒素与可溶性受体类似物两者的作用 将分析介导兔体液分泌的受体。 人源合成多肽免疫兔的实验研究 B链氨基酸序列会导致抗体被 测试其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。最后由双方共同完成 B链的特定化学修饰和通过对其的研究 B链突变体关于氨基酸位置的信息 涉及重要的B链功能将被确定。

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.