title: Targeting Mycobacterium tuberculosis topoisomerase I by small-molecule inhibitors.
abstract: We describe inhibition of Mycobacterium tuberculosis topoisomerase I (MttopoI), an essential mycobacterial enzyme, by two related compounds, imipramine and norclomipramine, of which imipramine is clinically used as an antidepressant. These molecules showed growth inhibition of both Mycobacterium smegmatis and M. tuberculosis cells. The mechanism of action of these two molecules was investigated by analyzing the individual steps of the topoisomerase I (topoI) reaction cycle. The compounds stimulated cleavage, thereby perturbing the cleavage-religation equilibrium. Consequently, these molecules inhibited the growth of the cells overexpressing topoI at a low MIC. Docking of the molecules on the MttopoI model suggested that they bind near the metal binding site of the enzyme. The DNA relaxation activity of the metal binding mutants harboring mutations in the DxDxE motif was differentially affected by the molecules, suggesting that the metal coordinating residues contribute to the interaction of the enzyme with the drug. Taken together, the results highlight the potential of these small molecules, which poison the M. tuberculosis and M. smegmatis topoisomerase I, as leads for the development of improved molecules to combat mycobacterial infections. Moreover, targeting metal coordination in topoisomerases might be a general strategy to develop new lead molecules.
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India.
authors.forename: Adwait Anand
authors.initials: AA
authors.lastname: Godbole
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India.
authors.forename: Wareed
authors.initials: W
authors.lastname: Ahmed
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India.
authors.forename: Rajeshwari Subray
authors.initials: RS
authors.lastname: Bhat
authors.affiliation: LigDCipher, San Mateo, California, USA.
authors.forename: Erin K
authors.initials: EK
authors.lastname: Bradley
authors.affiliation: Collaborative Drug Discovery, Burlingame, California, USA.
authors.forename: Sean
authors.initials: S
authors.lastname: Ekins
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India vraj@mcbl.iisc.ernet.in.
authors.forename: Valakunja
authors.initials: V
authors.lastname: Nagaraja
mesh_terms: D020816:Amino Acid Motifs; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D004247:DNA / Q000235:genetics; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D007099:Imipramine / Q000494:pharmacology; D009154:Mutation / Q000235:genetics; D020102:Mycobacterium smegmatis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D054852:Small Molecule Libraries / Q000494:pharmacology*; D059004:Topoisomerase I Inhibitors / Q000494:pharmacology*; D014376:Tuberculosis / Q000188:drug therapy / Q000382:microbiology
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D054852:Small Molecule Libraries; D059004:Topoisomerase I Inhibitors; D004247:DNA; D004264:DNA Topoisomerases, Type I; D007099:Imipramine