Fig. 2.

Binding of Topo IV to linear, (+) supercoiled, and (–) supercoiled DNA. (A) Reactions containing linear ³²P-labeled pUC18 (1.3 nM) were incubated in binding buffer and the indicated concentration of Topo IV for 20 min at 30°C. The fraction of DNA bound to Topo IV was determined by filter binding. (B) Topo IV binding to linear ³²P-labeled pUC18 was competed against unlabeled linear (○), (+) supercoiled (Sc) (▵), or (–) supercoiled (Sc) (□) DNAs. Error bars are the standard deviations of duplicate experiments.