Rifamycins (Rifs) are highly potent antibiotics that treat tuberculosis by targeting the causative pathogen’s, Mycobacterium tuberculosis (Mtb), RNA polymerase (RNAP). Rifamycin resistance has become a major issue that is caused by single point mutations in the Rif binding site. The drug resistant mutations also cause fitness defects for the bacterium; however, secondary mutations occur that compensate for the fitness defects. These compensatory mutations primarily occur adjacent to or in the putative guanosine tetraphosphate (ppGpp) binding site. ppGpp is an alarmone that is produced during the stress response of many bacteria, including Mtb. In Escherichia coli, ppGpp has been shown to have many different effects on the cell; one of them is binding to and inhibiting RNAP. Using E. coli as a model for Mtb, our lab has been working under the hypothesis that ppGpp binds to Mtb RNAP in the analogous site to that in the E. coli RNAP and that the compensatory mutations were disrupting ppGpp’s binding. There has been evidence that ppGpp is necessary for Mtb to become latent. We hope to utilize this and design a molecule to block ppGpp binding thus bacteria will stay active and be much easier to kill. I have performed both cross-linking and kinetics studies that confirm the binding and reduction of activity of the E. coli RNAP by ppGpp; however, the Mtb RNAP does not bind or respond to ppGpp.

Exploration of Mycobacterium tuberculosis RNA polymerase's putative ppGpp binding site as a potential therapeutic target

2019 Fall National Meeting

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