FIG 3.

The nicking activity of DndE is dependent on divalent metal cations but is not sensitive to phosphorothioate (PT) modification. (A) pUC19 (0.3 μg) was incubated with 6 μM DndE in the reaction buffer in the presence of different divalent metal cations. Then, the reaction mixture was analyzed by 1% agarose gel. Nt.BspQI-nicked and BamHI-linearized pUC19 served as controls. NA indicates that no divalent metal cation was added. (B, C) PT-modified and non–PT-modified pUC19 (0.3 μg) were incubated with 6 μM DndE in reaction buffer. Then, the reaction mixture was analyzed by 1% agarose gel electrophoresis and stained for imaging. OC, open circular DNA; L, linearized DNA; CCC, covalently closed circular DNA.