Investigations of the Putative Active Site of the Quorum Quenching Protein LsrG from Escherichia Coli and Purification of LsrE from Salmonella Typhimurium
Date of Award
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Bachelor of Arts
Chemistry & Biochemistry
Stephen T. Miller
Quorum sensing is a process in which bacteria coordinate gene expression in a cell-density dependent manner. Quorum sensing is facilitated by the secretion and importation of small signaling molecules called autoinducers. One class of autoinducer, termed autoinducer-2 (AI-2), facilitates interspecies communication. AI-2 consists of a set of interconverting derivatives of 4,5-dihydroxy-2,3-pentadione (DPD). In Escherichia coli and Salmonella typhimurium, AI-2 is internalized and processed by the proteins encoded for by the lsr operon. This process is thought to disrupt communication networks of neighboring species and therefore provide an evolutionary advantage. Since AI-2 signaling has been implicating in the coordinated gene expression of biofilm formation and virulent factors in several species, elucidating the mechanism by which bacteria process AI-2 could have several biotechnological and medical applications. In this study, I investigate two proteins on the lsr operon: LsrG and LsrE. LsrG has been shown to isomerize the phosphorylated version of AI-2 (P-AI-2) but the mechanism by which this reaction occurs is unknown. Therefore, I probe the putative active site of LsrG by x- ray crystallography and the creation of novel point mutants. LsrE is a nonconserved protein of the lsr operon that has not been characterized in vitro. I present the first attempts at expressing and purifying LsrE in high yield and purity for in vitro assays and x-ray crystallography.
Tanner, Samuel E. , '14, "Investigations of the Putative Active Site of the Quorum Quenching Protein LsrG from Escherichia Coli and Purification of LsrE from Salmonella Typhimurium" (2014). Senior Theses, Projects, and Awards. 216.