Preliminary structural analysis of activating nitroreductases of PA-824 compound and delamanid in Mycobacterium tuberculosis

Abstract

Mycobacterium tuberculosis (Mtb) is the responsible agent of one of the infect-contagious disease with highest mortality indices in the world. With about 9 million of new cases by year, the indices indicate that the occurrence of this disease was never so high, despite prophylaxis strategies such as BCG vaccine and chemotherapy treatment. In Brazil, tuberculosis also deserve attention, due to the more than 70,000 news cases diagnosed by year. Nowadays the treatment of tuberculosis consist in a long period of multi therapy treatment (between 6 to 9 months). This contemporary problematic becomes worse together with the emerging of resistant strains to antituberculosis drugs, which allow the arising of multi (MDR) and extensively drug resistant strains (XDR). This event increases the necessity of the scientific community to develop new drugs against M. tuberculosis in its active and latent stages. Among the drugs in development against tuberculosis, the nitroimidazole PA-824 are highlighted because its efficacy. Studies have shown that this compound is a pro-drug, which has a new mechanism of action, which is based in its bio-reduction by enzyme deazaflavin dependent nitroreductase (Ddn). However, there is a lack of information about the mechanism of interaction between PA-824 and Ddn because the structure for this whole enzyme is not known. Thus, the understanding how this enzyme work and what is mechanism of action of PA-824 are not completely described. In this project, we aim to contribute to the structural biology of Ddn and for the other homology enzymes, Rv1261c and Rv1558. For that, we intend to make new construct for the Ddn gene and for the homolog proteins. We also intend to perform the superexpression, purification, crystallization, and obtain preliminary data of X-ray diffraction. This preliminary work will contribute to obtain new structures that might give key insights to understand the action mechanism of nitroimizales.