Inhibition of gyrase-mediated DNA cleavage by levofloxacin (LVX) and nybomycin (NYB). DNA cleavage induced by wild-type (upper panel) and mutated (lower panel)
DNA gyrase from Staphylococcus aureus in the presence of either LVX (left) or NYB (right). Drugs at the indicated concentrations were mixed with supercoiled plasmid DNA
pTWV228 followed by addition of wild-type GyrA and GyrB or of mutated GyrA(Ser84Leu) and GyrB and were then incubated at 25 ◦C for 1 h. Detailed procedures are given in
Section 2.7. N, L and S represent the nicked, linear and supercoiled plasmid DNA, respectively. The appearance of nicked or linear DNA indicates that the antibiotic inhibited
the re-ligation step of DNA gyrase activity. The right parts indicate controls for the linear (L) and supercoiled (covalently closed-circular DNA; CCC) plasmid pTWV228.