Fig. 3.

Strand cleavage by Flp and Trp-330 mutants of Flp using H₂O₂ and tyramine as exogenous nucleophiles. Cleavage reactions were carried out on a 5' end-labeled substrate at 30°C using 1% H₂O₂ (A) or 100 mM tyramine (B) as exogenously supplied cleavage nucleophiles. The products of cleavage, indicated by ‘CP’, were separated from the substrate ‘S’ by denaturing polyacrylamide electrophoresis. In the kinetic assays, samples were quenched by addition of SDS to a final concentration of 0.2% for further processing and analysis. Band intensities were quantitated using a phosphorimager. The values plotted were from four independent assays.