European Journal of Biomedical and Pharmaceutical Sciences

EFFECT OF G67R AND G207E MUTATIONS ON STABILITY OF ARYLAMINE NACETYLTRANSFERASE IN ISONIAZID RESISTANCE STRAINS OF MYCOBACTERIUM TUBERCULOSIS REVEALED BY MOLECULAR DYNAMICS SIMULATION STUDY

Lingaraja Jena, Shraddha Deshmukh, Tapaswini Nayak, Gauri Wankhade, Bhaskar C. Harinath*

ABSTRACT

Isoniazid (INH) is a front line drug used in the treatment of tuberculosis (TB) that remains a major cause of death worldwide. Isoniazid is a prodrug, requiring activation in the mycobacterial cell by the catalase / peroxidase activity of the KatG whereas arylamine N-acetyltransferase (NAT), a drug-metabolizing enzyme of MTB (Rv3566c) can acetylates isoniazid by transferring an acetyl group from acetyl coenzyme A to the terminal nitrogen of INH. Two mutations in NAT enzymes (G67R and G207E) were reported in clinical isolates of MTB associated with INH resistance. To study the effect of these mutations on NAT, molecular dynamics (MD) simulation analysis was performed for both wild type and two mutant models of NAT. Additionally, we performed docking of INH with the foresaid models of NAT enzyme followed by MD simulation of respective protein-ligand complexes. We have found that the binding site pocket was more stable in NAT_G67R mutant and the residues of this mutant model fluctuate less in both bound and unbound cases. In mutant models, the alteration of Gly to Arg (G67R) or Glu (G207E) provides extra electrostatic interaction with neighboring amino acids which supports the stability of the binding interfaces. Thus the stability of the mutant models observed by computational approach, might help in enhanced acetylation of INH and detoxification, resulting in isoniazid resistance in addition to the over expression of the enzyme when exposed to the drug.

Keywords: NAT; isoniazid; Mycobacterium tuberculosis; mutation; Molecular Dynamics.