DNA-dependent ATPase and 3'-5' DNA helicase that may be involved in repair of stalled replication forks. Unwinds the lagging strand from forked DNA structures in a 3'-5' direction. PCNA, the DNA polymerase sliding clamp subunit, stimulates the helicase activity, and may alter substrate specificity. Unwinds branched DNA (Holliday junctions) in an ATP-dependent fashion; ss- and dsDNA stimulate ATPase to the greatest extent, although it preferentially binds DNA with a single-stranded region. Processes a RecA-mediated recombination intermediate between gapped circular and homologous linear dsDNA. ATP + H2O = ADP + H(+) + phosphate Divalent cations, Mg(2+) and Zn(2+) are best. Monomer. Interacts with PCNA. Constitutively expressed (at protein level). Belongs to the helicase family. Hel308 subfamily.