Structure of Proteins Involved in Bacterial Pathogenesis

细菌的发病至少包括两个步骤：1-细菌附着在被感染的宿主组织上，2-细菌分泌有毒分子。这两个步骤都是由细菌表面被称为“菌毛”的纤维结构介导的。在菌毛的一端（向外），含有一种叫做“黏附素”的蛋白质，它能特异性地与宿主表面的多糖结合。在另一端，菌毛可能附着在负责注射有毒物质的分泌机制上。菌毛本身是由几种不同的蛋白质亚基组成的复杂聚合物。在这篇论文中，我们建议研究1-菌毛的生物发生，2-细菌附着于宿主组织，3-蛋白质分泌的结构基础。我们以尿路致病性大肠杆菌P型菌毛为模型，研究菌毛的生物发生和细菌附着，以致溃疡幽门螺杆菌IV型分泌系统为模型，研究细菌对蛋白质的分泌。我们已经获得了几种毛菌亚基的晶体及其组装伴侣；我们还结晶了粘附素与同源多糖的二元配合物；最后，我们已经结晶了IV型分泌机制的重要组成部分。其中两个结构已经或正在被解决。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，将不仅对研究中的各种系统的基本知识产生影响，而且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.