Abstract

Antibiotic resistance is a growing issue worldwide, therefore there is a pressing need to find a new strategy to fight off bacterial infections. Anti-virulence is a strategy designed to disarm rather than kill bacteria, eliminating the bacteria’s evolutionary pressure to become resistant. One virulence factor target is the formation of biofilms. Biofilms are layers of bacteria within a hydrated matrix of polysaccharides and proteins enabling them to defend against antibiotics and the host immune system. Bacteria use quorum sensing to communicate through signaling molecules called autoinducers (AI), triggering gene expression changes which lead to biofilm formation. The AI-2 pathway operates in Gram-positive and Gram-negative bacteria, making it an attractive target for broad spectrum biofilm inhibition. The AI-2 signaling molecule derives from 4,5-dihydroxypentane-2,3-dione (DPD) which results from cleavage of S-ribosyl-L-homocysteine (SRH) by the S-Ribosylhomocysteinase enzyme, LuxS. The main goal of this research is to inhibit LuxS through covalent inhibition. To create a covalent inhibitor for the LuxS protein, molecules will be synthesized to mimic SRH with different electrophiles attached to react with the nucleophilic cysteine in the active site of LuxS. These inhibitors will be synthesized by coupling an electrophilic tail to L- homoserine. To test these inhibitors, LuxS was expressed and purified to be used in later enzyme-based inhibition assays. Computational docking was used to test the binding affinity of proposed inhibitor structures and guide the planning of other new potential inhibitors.

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