Date of Award

Spring 2017

Document Type

Thesis

Terms of Use

© 2017 Meghann R. Kasal. All rights reserved. This work is freely available courtesy of the author. It may only be used for non-commercial, educational, and research purposes. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts

Department

Chemistry & Biochemistry Department

First Advisor

Stephen T. Miller

Abstract

Bacterial cell-cell communication, known as quorum sensing, is a density-dependent phenomenon that regulates multicellular behaviors such as bioluminescence and virulence. Interspecies quorum sensing is mediated by a signal known as autoinducer-2 (AI-2), which belongs to a family of molecules derived from 4,5-Dihydroxy-2,3 pentanedione (DPD), a key metabolic product of the enzyme LuxS. AI-2 is recognized by many bacteria that belong to several phyla, including Enterobacteriaceae, Rhizobiaceae, and Bacillaceae, as a non-borated cyclic derivative of DPD known as (2R,4S)-2-methyl-2,3,3,4-tetrahydroxytetrahydrofuran (R-THMF). Building on previous research, we have recently identified several novel LsrB orthologs through sequence alignments and fold-prediction software. We showed that Thermobacillus composti and Clostridium saccharobutylicium have functional AI-2 receptors despite variations in the binding site residues as compared to known LsrB proteins. Furthermore, we obtained an X-ray crystal structure of C. saccharobutylicium LsrB which indicated that the binding site superimposes well onto a known receptor from Salmonella typhimurium. We optimized a purification protocol for each receptor and have begun to conduct ITC experiments to assay the differences in binding affinity across species and to determine which residues are critical for AI-2 recognition. Finally, crystallization trials have identified potential conditions to yield crystals T. composti LsrB, which will be explored in the future to elucidate the protein-ligand binding interactions.

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