Determination of the structural bases for resistance to first-line drugs using missense mutations in Mycobacterium tuberculosis

Abstract

Tuberculosis is a serious problem of public health because of the number of deaths caused by the disease and also by the number of resistant and multiresistant strains to all in use drugs. Among the key medicines used in the treatment of tuberculosis, isoniazid (INH) and pyrazinamide (PZA) are the first-line drugs, together withethambutol (EMB) and rifampicin (RIF). Recently, it has been reported that fluoroquinolones such as moxifloxacin (MFX) may be used together with first-line drugs to decrease even more the treatment time. In addition, other antimicrobials,such as ethionamide (ETH) are only used in multi-resistance cases, and they are considered as the second line compounds. Interestingly, for INH and PZA, their targets, which are the enzymes InhA, PanD and DNA gyrase, respectively, have thecharacteristic to have missense mutations. However, the molecular mechanisms of resistance caused by these mutations are not sufficiently studied. In this project, we selected a number of missense mutations observed in the coding region of inhA, panD and gyrA and gyrB found in clinical isolates from many countries, including Brazil, which had not been thoroughly characterized, neither biophysical nor biochemically. We intend with this project, to obtain the mutant proteins and perform studies aiming to determine their structures, functional and biophysical analysis in the presence of substrates and adducts, as well as perform in silico studies to determine the effect of the mutations on the structure and dynamics of the targets. The integration of all these results will allow us to have a better understanding of the effect of these mutations on the affinity and structure. With this study, we expect to contribute to understanding the molecular basis of these mutations, which might contribute in the future to a more personalized treatment and also in proposing new therapies and/or the development of new antituberculosis drugs. (AU)