| Tuberculosis (TB) is the leading cause of death in the world from a single infectious agent. Approximately two million people each year die of tuberculosis, and currently one-third of the world's population is infected with Mycobacterium tuberculosis, the causative agent of the disease. Immunization with an attenuated strain of the related bacterium, M. bovis BCG is used in most of the world; its effectiveness in preventing most forms of TB is limited at best. Because treatment of TB depends upon drug treatment, it is not surprising that certain strains of M. tuberculosis have evolved resistance to the standard chemotherapeutic drugs. In light of this, new effective drugs are desperately needed. My dissertation describes experiments that explore a novel target for TB treatment: the biosynthesis of the essential nucleic acid component, thymidine. Specifically, I will examine as potential drug targets the two interconnected pathways used by M. tuberculosis to synthesize thymidine. First, I will detail my experiments testing experimental inhibitors of dihydrofolate reductase, a key enzyme in the well-known classical thymidine synthesis pathway. Second, I will analyze the mechanisms by which resistance to these experimental inhibitors could evolve and the frequency with which this occurs in vitro. Finally, I will examine the newly identified alternative pathway of thymidine synthesis, and describe the mutational analysis of structure and function of the key enzyme in this alternative pathway, ThyX. |
