Structural Interactions of Bacterial Adhesin with Glycosaminoglycans

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DESCRIPTION (provided by applicant): Antibiotic resistance is becoming an imminent health threat. One strategy for combating this is to inhibit the adhesion of microbes to human cells. However, specific structural interactions between microbes and target cells are not well characterized, thus hampering the development of new anti-microbial agents. This proposal strives to overcome this deficiency by conducting an in-depth structural study of the interactions between bacterial adhesins and glycosaminoglycans (GAGs), a ubiquitous polysaccharide found on the surface of cells and a primary target for bacterial adhesins. The focus of the proposal will be on the decorin binding protein (dbp), an adhesin from Borrelia burgdorferi, the etiological agent of Lyme disease. To study the interactions between GAGs and dbp, the structures of dbp in both cytoplasmic and its native lipoprotein form will be solved using solution NMR. Using these structures as bases, dbp's interactions with heterogeneous and homogeneous GAG oligomers will be determined. The main goal of this research is to obtain high resolution structures of dbp complexed to GAG and deduce from these structures the specific interactions between GAG and dbp that can be targeted to prevent the adhesion of bacteria to human cells. Finally, as GAGs often exist in the form of proteoglycans, an attempt will be made to characterize the interactions between dbp and intact decorin, the proteoglycan that dbp primarily targets. The main goal for this portion of the proposal will be to construct the complex structure of dbp with intact decorin utilizing only NMR derived orientational restraints and the dimeric nature of intact decorin. The proposed work will be carried out at the Complex Carbohydrate Research Center, a multidisciplinary research institute and one of the country's premier glycobiology research centers. The candidate's long term career goal is to understand the rules governing the interactions of GAGs with its protein targets and devise strategies for steering these interactions in a desired direction. The candidate's immediate goal during the mentored phase will be to acquire proficiency with the chemical and biochemical methods used to purify GAG oligomers and learn the use of mammalian expression systems that will be crucial for obtaining intact decorin. The knowledge of these techniques will enable the candidate to conduct independent research in the proposed area. Relevance: The results of this proposal will be invaluable for the design of a new class of anti-microbial agents that specifically inhibits the adhesion of microbials to human cells. It also adds to our understanding of how sulfated polysaccharides interact with proteins to initiate important biological events.