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Fluoroquinolones exhibit very good activity against Mycobacterium tuberculosis (M.tb) and other mycobacterial species. These antibiotics act by binding to complexes of bacterial DNA and DNA gyrases, thereby interfering with DNA replication. Now, researchers have identified an M.tb protein that confers fluoroquinolone resistance via a novel mechanism.
These investigators isolated the M.tb homologue of a protein that produces fluoroquinolone resistance in Mycobacterium smegmatis. In vitro, this protein, termed MtMfpA, inhibited both ATP-dependent supercoiling and ATP-independent relaxation reactions catalyzed by Escherichia coli DNA gyrase. Crystallographic analysis revealed a DNA-like helical structure with a strongly negatively charged face …