498 Structural Determination of the CqsR CACHE Domain and its Autoinducer

Abstract

OBJECTIVES/GOALS: Our goal is to determine the structure of the CACHE domain of the Vibrio cholerae quorum sensing receptor CqsR as well as its autoinducer (AI). We are performing X-ray crystallography on the protein in its apo form, with the fractions containing the AI, and with known ligand ethanolamine (ETA). METHODS/STUDY POPULATION: We have transformed BL21(DE3) E. coli cells with a pTB146 vector to contain the gene for the CqsR CACHE domain. We grow these cells to high optical density and induce protein expression, at which point we harvest them and purify the protein. This entails lysing the cells, separating the protein with Ni-NTA resin, cleaving our protein tag, and column chromatography. With purified protein, high-throughput screens are set up to find crystallization conditions of apo CqsR, CqsR-ETA, and CqsR-AI. We then determine conditions that best lead to crystal formation and optimize them. Crystals are then diffracted with X-rays, process the data, and determine the structure of protein and AI. RESULTS/ANTICIPATED RESULTS: We anticipate finding the structure of the CqsR CACHE domain to a high resolution in addition to the identity of its autoinducer. Previous results found that the structure is homologous to another V. cholerae chemoreceptor, Mlp37, and we expect the results from this project to confirm this. In addition, we know that the autoinducer weighs approximately 62 daltons, the same as the known ligand, ethanolamine. Given that CACHE domains bind specifically to their ligands, we anticipate that the autoinducer will be structurally similar to ethanolamine. DISCUSSION/SIGNIFICANCE: The results will reveal the structure of the CqsR CACHE domain and its autoinducer. This knowledge will better allow researchers to treat cholera, as both autoinducer identity and receptor conformational changes will be uncovered, allowing for drug development to inhibit cell growth.