Rate of DNA cleavage with various FokI concentrations. The conditions of DNA cleavage reaction are described in Fig. 2. Samples were withdrawn at the indicated times from the reactions that contained 0.1 nM FokI (■), 0.2 nM FokI (♦), 0.4 nM FokI (•), 0.6 nM FokI (▴), 0.8 nM FokI (▾), and 1.0 nM FokI (∗). The amount of cleaved DNA was determined as in Experimental Procedures. (Inset) Initial velocity vs. FokI concentration.