An ATP, Mg(2+)-dependent DNA 3'-5' and 5'-3' helicase that may be involved in repair of stalled replication forks. Stimulated by both ss and dsDNA. Unwinds both leading and lagging strands in replication fork structures, unlike orthologs in P. furiosus and M. thermautotrophicus which only unwind the lagging strand and only have 3'-5' helicase activity. Preferentially binds dsDNA with overhangs or branched DNA. Able to anneal DNA substrates that could form a replication fork-like structure, has replication fork reversal activity (at least in vitro). ATP + H2O = ADP + H(+) + phosphate Helicase activity is inhibited by Hjc (PubMed:18296528) and by PCNA123 and PCNA323 (PubMed:18782564). Monomer; forms a 1:2 complex with Hjc, which may form a complex with Holliday junction DNA. DNA-binding occurs via the first 2 N-terminal domains, which are also responsible for ATPase. The central region (432-645) which is structurally composed of 2 domains (432-500 and 501-645) is necessary for helicase activity. The C-terminal region (646-704) inhibits ATPase and helicase activity. Belongs to the helicase family. Hel308 subfamily.