Figure 2.

Stimulation of RECQ5β helicase activity on oligonucleotide-based partial duplexes by ssDNA-binding proteins. (A) Unwinding of 1 nM 30-bp forked duplex, ³²P-end labeled in the 5′-ssDNA arm, by RECQ5β at concentrations ranging from 0 to 320 nM. Reactions were incubated at 37°C for 20 min, and the products were analyzed by 10% nondenaturing PAGE. Radiolabeled species were visualized by autoradiography. (B) Unwinding of 1 nM 30-bp forked duplex by 20 nM RECQ5β in the presence of the indicated concentrations of RPA. Reactions were carried out and analyzed as in (A). (C) Kinetics of unwinding of 1 nM 30-bp forked duplex by 20 nM RECQ5β in the presence of 24 nM RPA, 120 nM E. coli SSB or without any ssDNA-binding protein. The percentage strand displacement was estimated as described in Materials and methods.