Using Synthetic Ligands to Activate a Global Regulator Protein in Endospore-Forming Bacteria

Science Center, Bent Corridor

Many bacteria belonging to the Gram-positive branch, such as Bacillus subtilis and Clostridium difficile, are capable of forming dormant, environmentally-resistant spores under conditions of nutrient deficiency. To avoid initiating sporulation unnecessarily when nutrients are in excess, various specific and global regulators are required. CodY is a regulatory protein found in most Gram-positive bacteria; it is active under nutrient-rich conditions and represses sporulation and metabolic pathways for utilization of secondary nutrients when primary nutrients are in excess. In C. difficile, CodY also represses the synthesis of the major virulence factors (toxins A and B). The aim of this project is to identify compounds that bind to and activate CodY in order to repress virulence. If CodY could be made constitutively active, even under conditions of low nutrient availability, spore-formation and toxin expression would continuously be repressed. This would be advantageous when picking a drug target for more virulent strains of Gram-positive bacteria. We hypothesize that compounds that are similar to the two natural ligands, GTP and the branched-chain amino acids (BCAAs), will activate CodY. While some analogs of these ligands, or binding molecules, are commercially available, they are not optimal because they might negatively interfere with the host’s natural biochemistry. Thus alternative synthetic ligands must be tested. We will screen for synthetic ligands that have binding abilities similar to those of the natural ligands via gene activity analysis. Our results suggest a plant compound may give insight into potential substitutes that affect CodY activity without being detrimental to the human host.