Structure of Proteins Involved in Bacterial Pathogenesis

细菌的发病机制涉及至少两个步骤：1-细菌附着于待感染的宿主组织，以及2-细菌分泌毒性分子。 这两个步骤都是由细菌表面的纤维结构介导的，称为“菌毛”。 在菌毛的一端（向外），菌毛含有一种称为“粘附素”的蛋白质，它特异性地结合宿主的表面多糖。 另一方面，菌毛可能附着在负责注入有毒物质的分泌机器上。 菌毛本身是几种不同蛋白质亚基的复杂聚合物。 在这个建议中，我们建议研究1菌毛生物发生，2细菌附着到宿主组织，和3蛋白分泌的结构基础。 我们已经使用了P型皮利的尿路致病性大肠杆菌作为一个模型，研究菌毛的生物发生和细菌的附着，我们已经使用了IV型分泌系统的溃疡引起的幽门螺杆菌作为一个模型，研究蛋白质的分泌细菌。 我们已经获得了几个晶体的菌毛亚基在复杂的组装伴侣，我们也结晶二元复合物的粘附素与其同源多糖，最后，我们结晶的重要组成部分IV型分泌机械。 其中两个结构已经或正在解决。 我们的建议，通过寻求了解细菌致病性的结构基础，负责重要的传染病，将不仅对正在研究的各种系统的基础知识的影响，但也将有助于设计抗生素化合物，有效地对抗这些疾病。

Bacterial pathogenesis involves at least two steps: 1- attachment of the bacteria to the host tissue to be infected, and 2- secretion of toxic molecules by the bacteria. Both steps are mediated by a fibrous structure displayed at the surface of the bacteria called a "pilus". On one end of the pilus (facing outwards), the pilus harbours a protein called "adhesin" which binds specifically to the host's surface polysaccharides. On the other end, the pilus may be attached to a secretion machinery responsible for injection of toxic substances. The pilus itself is a complex polymer of several different protein subunits. In this proposal, we propose to study the structural basis of 1- pilus biogenesis, 2- bacterial attachment to the host tissue, and 3-protein secretion. We have used the type P pili of uropathogenic Escherichia coli as a model to study pilus biogenesis and bacterial attachment, and we have used the type IV secretion system of the ulcer-causing Helicobacter pylori as a model to study the secretion of proteins by bacteria. We have obtained several crystals of pilus subunits in complex with their assembly chaperone; we have also crystallized binary complexes of adhesins with their cognate polysaccharides; and finally, we have crystallized important components of the type IV secretion machinery. Two of these structures have been or are in the process of being solved. Our proposal, by seeking to understand the structural basis of pathogenicity in bacteria responsible for important infectious diseases, will have not only an impact on the fundamental knowledge of the various systems under study, but will also help design antibiotic compounds which are effective in the fight against these diseases.