Figure 3.

Kinetics of Flp strand cleavage activity and type I Flp endonuclease activity in half-site substrates. In the schematic representations of half-site substrates, the asterisk indicates ³²P-label at the 5′-end, ‘P' the scissile phosphate and ‘mp' the scissile methylphosphonate. Reactions were analysed by PAGE for covalent Flp-DNA adduct (line ending in a circular knob) formed by strand cleavage (A) and by denaturing PAGE for hydrolysis (23-mer). (B) The hydrolysis product from the P-half-site runs as a doublet band (left panel in B), whereas that from the MeP-half-site (right panel in B) runs almost exclusively as a single band. The end-labelled half-site (A) or its labelled strand (B) is denoted by ‘S'. The plot below represents mean values from three separate experiments.