Figure 5. Cleavage/religation equilibrium.

(A) Gel electrophoresis of the products from the incubation of Top1 with the [γ -³²P] end-labelled duplex DNA (CL25/CP25), shown at the top of the Figure. The arrow indicates the preferred cleavage site. The duplex was incubated for 1 or 2 min with the enzyme (lanes 1 and 2), in presence of CPT (lanes 3 and 4), Et-KuQ (lanes 5 and 6), after a pre-incubation with CPT and then addition of Et-KuQ (lane 7) and after pre-incubation with Et-KuQ and then addition of CPT (lane 8). Lane 9, no enzyme added. The band corresponding to the enzyme-substrate cleaved complex is indicated by an asterisk. (B) Percentage of the cleavable complex normalized to the total radioactivity of each lane.