FIG. 4.

DNA cleavage patterns generated by gyrase^WT and mutant GyrA^S83W in the presence of the quinolones CP-115,953 and ciprofloxacin. The same DNA fragments presented in Fig. 3 were used. The left-hand panel shows labeling of the upper DNA strand; the right-hand panel shows labeling of the lower DNA strand. Drugs and enzymes are indicated above each lane. Concentrations were 100 μM for CP-115,953 and ciprofloxacin, respectively. Cleavage reactions were performed at 25°C for 2 h in the presence of 5 mM MgCl₂. Purine ladders were obtained after formic acid reaction. Lanes: Control, no Top2p, no drug treatment; Gyr WT: gyrase^WT from E. coli; GyrA^S83W, mutant Ser⁸³Trp gyrase. Numbers correspond to genomic positions of the nucleotide covalently linked to Top2p. Double-headed arrows correspond to DNA cleavage sites with a 4-bp stagger that represent potential DNA double-strand breaks.