Critical role in recombination and DNA repair. Helps process Holliday junction intermediates to mature products by catalyzing branch migration. Has a DNA unwinding activity characteristic of a DNA helicase with a 3'- to 5'- polarity. Unwinds branched duplex DNA (Y-DNA). Plays a role in recovery after DNA ADP-ribosylation. ATP + H2O = ADP + H(+) + phosphate Significantly reduced survival of cells expressing DNA ADP-ribosyl transferase (darT) mutant G49D. Belongs to the helicase family. RecG subfamily.