Structure of Proteins Involved in Bacterial Pathogenesis

细菌的致病至少涉及两个步骤：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显示的一种纤维结构介导的，这种结构被称为“菌毛”。在菌毛的一端(面朝外)，菌毛含有一种名为“粘附素”的蛋白质，它专门与宿主的表面多糖结合。在另一端，菌毛可以连接到负责注射有毒物质的分泌机器上。菌毛本身是由几个不同的蛋白质亚基组成的复杂聚合物。在这项建议中，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-蛋白质分泌的结构基础。我们以泌尿系致病性大肠杆菌的P型菌毛为模型研究菌毛的生物发生和细菌附着，并以引起溃疡的幽门螺杆菌的IV型分泌系统为模型研究细菌分泌蛋白质的情况。我们已经得到了几个菌毛亚基与它们的组装伴侣形成的络合物的晶体；我们还结晶了粘附素与它们的同源多糖的二元络合物；最后，我们结晶了IV型分泌机械的重要部件。其中两个结构已经或正在解决。我们的建议，通过寻求了解导致重要传染病的细菌致病性的结构基础，不仅将对正在研究的各种系统的基本知识产生影响，而且还将有助于设计有效地抗击这些疾病的抗生素化合物。

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.