Figure 3

Optimal pH, temperature and Mg(II) and Mn(II) ion concentrations for the dsDNA exonuclease activities of SXT-Exo, as determined by quenched PicoGreen Assays. Panel A: Optimum Mg²⁺ ion concentrations. SXT-Exo (2 pmol of trimers) in Tris-HCl (25 mM, pH7.4), 50 mM NaCl containing MnCl₂ (0-10 mM); was incubated with PstI-linearized pUC18 (5 ng, 0.003 pmol) at 37°C for 30 mins. Panel B: Optimum Mn²⁺ ion concentrations. SXT-Exo (2 pmol of trimers) in Tris-HCl (25 mM, pH7.4), 50 mM NaCl containing MgCl₂ (0-50 mM); was incubated with PstI-linearized pUC18 (5 ng, 0.003 pmol) at 37°C for 30 mins. Panel C: Optimum pH. SXT-Exo (2 pmol of trimers) in Tris-HCl (50 mM, adjusted to pH 7.0-9.0), 50 mM NaCl, 0.5 mM MnCl₂; was incubated with PstI-linearized pUC18 (5 ng, 0.003 pmol) at 37°C for 30 mins. Panel D: Optimum temperature. SXT-Exo (6 pmol of trimers) in Tris-HCl (25 mM, pH 7.4), 50 mM NaCl, 0.5 mM MnCl₂; was incubated with PstI-linearized pUC18 (5 ng, 0.003 pmol) at 37°C for 1 min. Graphs show the the mean values ± standard deviation. See methods for detailed experimental procedures.