Figure 5.

Strand preference. The reactions in SfiI assay buffer at 30°C contained SfiI endonuclease and one of the following oligoduplexes at 0.2 µM: (A) AACAA; (B) AAACA. For the reactions in (A), the concentration of SfiI was 0.5 nM and the AACAA was 5′-end-labelled with ³²P in either the top strand (data points marked by inverted triangles) or the bottom strand (marked by triangles). For the reactions in (B), the concentration of SfiI was 0.1 nM and the AAACA was 5′-end-labelled with ³²P in either the top strand (data points marked by open circles) or the bottom strand (marked by closed circles). At timed intervals after adding SfiI, samples were withdrawn from the reactions and analysed as in the Materials and Methods to determine the percentage of each substrate that had been cleaved in the labelled strand.