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) (By similarity). ATP + H2O = ADP + H(+) + phosphate Belongs to the helicase family. RecG subfamily.