DndE crystal structure comparison and nicking activity determination. (A) Sequence alignment of DndE from N. bangense JCM10635 and E. coli B7A with the structural elements labeled on the top. (B) Structural comparison of N. bangense JCM10635 DndE and E. coli B7A DndE. DndE from N. bangense JCM10635 is in purple, and that from E. coli B7A is in cyan. (C) DNA-nicking activity of DndE; 0.3 μg of pUC19 was incubated with 6 μM DndE for 1 to 12 h, and Nt.BspQI-nicked and BamHI-linearized plasmids served as controls. OC, open circular DNA; L, linearized DNA; CCC, covalently closed circular DNA.