FIG. 1.

Effects of ATP and MgCl₂ on the binding of P143 to 252-bp hr5 ss- and dsDNA. The conditions for purification of P143, radiolabeling of hr5 probe, and EMSAs have been described previously (12). In this experiment, the molar ratios of enzyme to probe were 10:1 and 50:1. The presence or absence (+ or −) of 2 mM ATP and 6 mM MgCl₂ is indicated at the top. Lanes 1 to 7 contain dsDNA probe; lanes 8 to 14 contain ssDNA probe. ssDNA probe was generated from the double-stranded probe by dilution in water followed by boiling and rapid cooling on ice. Free and protein-bound DNAs were separated on a 3.5% acrylamide–Tris-borate-EDTA gel, dried, and exposed to PhosphorImager plates. ds, double-stranded; ss, single-stranded.