DNA-dependent ATPase and 3'-5' DNA helicase that may be involved in repair of stalled replication forks. Helicase with 3'-to 5'- polarity; able to unwind over 100 bp of DNA at 50 degrees Celsius. Unwinds forked DNA, preferentially on lagging strand forks; has weaker activity on Holliday junctions. Displaces the invading strand in DNA D-loops. Unwinds short oligonucleotides from dsDNA with 3'- but not blunt ends or 5'-ssDNA tails in an ATP-dependent manner. ATPase activity is stimulated by ssDNA but not dsDNA, protein binds ssDNA, dsDNA with 5'- or 3'-overhangs but not blunt ended dsDNA and replication forks. Replication forks bind both this protein and RPA. RPA does not stimulate the helicase activity of this protein. ATP + H2O = ADP + H(+) + phosphate Monomer (By similarity). Binds replication protein A (RPA), in presence and absence of DNA. The C-terminal region (about 633-690) acts as a brake for ATP hydrolysis (PubMed:17991488) and interacts with RPA (PubMed:21195035). Belongs to the helicase family. Hel308 subfamily.