Protein Target Identification and Characterization for Antibiotic Discovery

The persisting threat of antibiotic-resistant-pathogen infection is a serious peril for medicine. Most bacteria are now resistant to current antibiotics. We now need to identify new drug targets, new bioactive molecules and to develop second generation of antibiotics. Using high throughput screening toward PurE enzyme inhibition, 1, 3, 4 oxadiazole compounds were found to be active against a wide range of pathogens. However, the MIC values of most compounds were lower than the IC50 values against PurE enzyme, suggesting that the compounds interact with a second target. By using mutant selection, we identified mutations in a protein we called TetR-PK, a protein with the potential of regulating the adjacent divergent gene, YhgE. In another project, resistant mutations were identified in the target fabI gene, using error prone PCR method that may serve as the bases for the development of a second generation of triclosan as well as other inhibitors of FabI. In the last project, an extensive biochemical and biophysical characterization of homologous PurE enzymes from Bacillus anthracis, Francisella tularensis and Yersinia pestis revealed a significant difference in the hydrophobic pockets on the surface of the three enzymes, and this difference may be exploited for narrow spectrum antibiotic development. Similarities of theses enzymes were also identified that can be exploited for broad spectrum antibiotic development. These findings constitute a framework for a new class of antibiotic development, the development of the next generation of FabI inhibitors as antibiotics and the exploitation of new features in an essential enzyme PurE of three pathogens.