The fluoroquinolones target the DNA gyrase (DNAG), a tetrameric enzyme which unwinds DNA by forming and re-ligating double stranded DNA breaks prior to transcription and replication (Fig. ). Specifically, two fluoroquinolone molecules intercalate into DNA breaks and bind specific gyrA residues via a coordinated Mg 2+ ion. This stabilizes DNA-DNA gyrase covalent linkages and prevents re-ligation of DNA double stranded breaks.