Kinetics of Methylation by EcoP1I DNA Methyltransferase
Figure 5
DNA methylation by M.EcoP1I in the presence of two metal ions. (a) Methylation by M.EcoP1I was measured by keeping the total divalent metal ion concentration at 6 mM, that is, from Ca2+ (6 mM) on the left to Mg2+ (6 mM) on the right (). pUC19 supercoiled DNA (1 M) was incubated with M.EcoP1I (400 nM) in the presence of varying concentrations of metal ions; Ca2+ and Mg2+ in methylation buffer and assays were performed as described in Materials and Methods. Methylation assays in the presence of Mg2+ () and Ca2+ (▾) alone are plotted. The plot with open triangle indicated sum of Mg2+ and Ca2+ concentration dependences. (b) Methylation assays were performed in the presence of Mg2+ and Zn2+ to a final concentration of 6 mM. pUC19 plasmid DNA (1 M) was incubated with M.EcoP1I (400 nM) in the presence of varying concentrations of metal ions, Mg2+ and Zn2+ in methylation buffer without metal ions.
