Fig. 2

Strand preference of F-CphI. a Purified F-CphI (1600 nM) was used to digest plasmid DNA (5 nM) in the standard endonuclease assay buffer for different times. Closed-circular plasmid DNA (C) was nicked to form open circular DNA (O) and then nicked again on the other strand to form a linear product (L). b Time course activity assay on ³²P-labeled oligonucleotide duplex. Oligonucleotides SBM4-60Top and SBM4-60Top-r were used to create a 60 bp duplex containing the F-CphI recognition site from the cyanophage S-BM4 psbA gene. The duplex was labeled on the top or the bottom strand by ³²P. Labeled duplex substrates were digested by F-CphI and the cleavage products were separated by electrophoresis on a 4% denaturing polyacrylamide gel. Substrates labeled on the top or the bottom strand were examined separately. Percent cleavage products are shown over time