Figure 4. In vitro DNA binding of IntI1 with free single-stranded attC (A) and attI (B) recombination sites.

Free 5′ ³²P radiolabeled ssDNA fragments containing recombination sites (0.1 pmoles) were incubated with purified IntI1 (5–10 pmoles) at 4°C for 20 min before electrophoresis on 1% agarose gel run at 50 V, for 2 hours at 4°C. Arrows indicate the protein-DNA complexes and F corresponds to free recombination sites.