دانلود رایگان مقاله انگلیسی نقش جهش های ژن pncA W68R و W68G در مقاومت پری زینامید - وایلی 2017

Abstract

Mycobacterium tuberculosis (Mtb) resistance towards anti-tuberculosis drugs is a widespread problem. Pyrazinamide (PZA) is a first line antitubercular drug that kills semi-dormant bacilli when converted into its activated form i.e. pyrazinoic acid (POA) by Pyrazinamidase (PZase) enzyme coded by pncA gene. In this study, we conducted several analyses on native and mutant structures (W68R, W68G) of PZase before and after docking with the PZA drug to explore the molecular mechanism behind PZA resistance caused due to pncA mutations. Structural changes caused by mutations were studied with respect to their effects on functionality of protein. Docking was performed to analyze the protein-drug binding and comparative analysis was done to observe how the mutations affect drug binding affinity and binding site on protein. Native PZase protein was observed to have the maximum binding affinity in terms of docking score as well as shape complementarity in comparison to the mutant forms. Molecular dynamics simulation analyses showed that mutation in the 68th residue of protein results in a structural change at its active site which further affects the biological function of protein i.e. conversion of PZA to POA. Mutations in the protein thereby led to PZA resistance in the bacterium due to the inefficient binding. This article is protected by copyright.

Conclusion

Due to increasing emergence of drug-resistant Mtb strains, present conventional therapies are rendered ineffective. Understanding the effect of gene mutation on structure of protein and its affinity for the ligand is required to aid the knowledge of drug development. This study is based on comprehensive analysis of the PZA drug resistance in Mycobacterium tuberculosis due to pncA gene mutations. Binding pocket determination, shape complementarity computation, molecular docking, molecular dynamics simulation and essential dynamic studies have been performed. Docking of the native protein showed best complementarity between the receptor and ligand. The protein trajectories showed that there was increased flexibility in the mutant protein atoms. The mutant proteins were loosely packed, less compact and show lower stability. All the analyses showed that the protein had lost its compactness and stability because of the mutation. The H-bond and hydrophobic interactions between the receptor and ligand were different for the native and mutant proteins affecting the protein-drug interaction. The mutant W68G protein was found to drastically affect the structure of binding site of protein. The protein-drug interaction was inefficient due to the structural change resulting in PZA drug resistance in Mycobacterium tuberculosis. Mutation in the 68th residue led to a structural change in the binding site of protein, thus PZA was not converted to its active form that renders it ineffective for TB treatment.