Figure 5.

Activity of vTopo with MC^ns, a MC that does not contain a consensus cleavage site. (A) Single-turnover cleavage and supercoil unwinding. The gel image shows the time course for relaxation of 10 nM MC^ns by 80 nM vTopo (S is the supercoiled substrate and P the relaxed product). MC^ns was also reacted with 20 (△), 40 (□), or 80 nM vTopo (○). The data were fit to a first-order rate equation. The values of k_lim were plotted vs enzyme concentration and were linear with respect to enzyme concentration over the accessible range (inset). Some error bars have been omitted for the sake of clarity but are similar to those shown. (B) Steady-state turnover under initial rate conditions. The relaxation of 2.5 nM MC^sp in the presence of 1 nM vTopo is shown in the gel image.