Effect of ATP on NurA nuclease activity.

<p>(A) NurA activity has been tested on a circular double-stranded DNA in the absence (lane 2) or in the presence (lane 3–6) of increasing concentrations of ATP (1.5 3, 5, 7 mM). A sample in which no protein was added in the mixture has been loaded and used as control (lane 1). (B) Analysis of ATP effect on NurA nuclease on linear single-stranded substrates. NurA nuclease activity on ODN1 (left) or ODN2 (right) was tested in the absence (lane 2) or in the presence (lanes 3–5) of increasing concentrations of ATP (from 2.5 to 10 mM). Lane 1 refers to a control in which no protein was added in the sample assay. (C) ATP seizes Mn²⁺ ions from the reaction. NurA endonuclease activity has been analyzed with increasing amounts of Mn²⁺ ions in the absence (lanes 2–7) or in the presence (lanes 8–13) of ATP (5 mM). The concentration of Mn²⁺ used is reported on the top of the gel. (D) Effect of EDTA on NurA nuclease activity. NurA nuclease activity on ODN2 has been analyzed, using 9 pmoles of NurA, in the presence of increasing amounts of EDTA or ATP as control (both from 2.5 to 10 mM), lanes 3–5 and 6–8, respectively. A control in which no protein was present was loaded on lane 1, while lane 2 refers to NurA nuclease activity in the absence of neither ATP nor EDTA.