Figure 5
Relaxation activity assay of H139C, Y174C and K524C mutants of MtTOP1. Serial dilutions of purified wild-type MtTOP1 and mutant derivatives with cysteine substitutions at H139, Y174 and K524 were added to 20 μL reaction volume of 10 mM Tris-HCl, pH 8.0, 50 mM NaCl, 0.1 mg/mL gelatin, 6 mM MgCl2 and 0.2 μg of supercoiled plasmid DNA. Incubation was at 37°C for 30 min.