Journal: Nucleic Acids Research
Article Title: Structure-based functional identification of Helicobacter pylori HP0268 as a nuclease with both DNA nicking and RNase activities
Figure Lengend Snippet: Nicking endonuclease activity of HP0268. (A) The nicking endonuclease activity at various protein concentrations (1, 2, 4 and 8 μM) after incubation at 37ºC for 30 min. OC, RC and linear are abbreviations for the nicked open-circular, relaxed circular and linear DNA, respectively. (B) The pH dependence of the DNA nicking activity. The substrate plasmid DNA was incubated with 4 μM HP0268 at 37ºC for 30 min under various pH conditions (pH 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0 and 9.5). (C) Effect of metal ions on the DNA nicking activity of HP0268. The substrate plasmid DNA was incubated with 4 μM HP0268 at 37ºC for 30 min in the presence and absence of 1 mM metal ion (Ca 2+ , Co 2+ , Ni 2+ , Fe 3+ , Mn 2+ , Mg 2+ and Cu 2+ ). Increasing concentrations (0.2, 0.4 and 1 μM) of Mn 2+ ion were used. Excess EDTA was used to remove the residual metal ions during the protein preparation. (D) The percentages of the resulting DNA conformations were plotted with regard to metal ion used. Cont. represents the substrate plasmid pET-21a(+) without HP0268, and Nt.BsmAI and NdeI represent the positive controls for the nicked and linear DNA, respectively. Commonly, 10 units of control enzyme were used in a final volume of 30 μl.
Article Snippet: Each band was identified as one of the DNA conformations by comparing the reference bands that were generated by the commercial enzymes Nt.BsmAI (a nicking enzyme) and NdeI (a restriction enzyme).
Techniques: Activity Assay, Incubation, Plasmid Preparation, Positron Emission Tomography