Date of Award

Spring 2016

Document Type

Restricted Thesis

Terms of Use

© 2016 Emily Gale. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts


Chemistry & Biochemistry Department

First Advisor

Stephen T. Miller


Both Gram-positive and Gram-negative bacteria use cell-to-cell communication to regulate a variety of multicellular functions such as bioluminescence, biofilm formation, and virulence. This process, termed quorum-sensing, requires the synthesis and recognition of hormone-like molecules called autoinducers. A particular autoinducer, autoinducer 2 (AI-2), is synthesized and recognized by many species of bacteria. This study focuses on the binding properties of the protein LsrR: a transcriptional repressor of the lsr operon, which is regulated by AI-2. Previous research has suggested that dihydroxyacetone phosphate (DHAP), a key metabolite, interacts directly with LsrR to repress transcription of the lsr operon. Here I report an optimized purification protocol for an N-terminal truncated version of LsrR (C-LsrR), attempt to crystallize C-LsrR, and begin to develop protocols to assess potential binding between C-LsrR and DHAP. Our initial approach of using intrinsic tyrosine fluorescence to quantify binding based on the protein's conformational changes was more difficult than expected. We then used a DHAP Assay Kit to measure unbound DHAP in solution before and after exposure to C-LsrR. Both methods seemed promising but need improvement before they will yield conclusive results.