The RuvA-RuvB complex in the presence of ATP renatures cruciform structure in supercoiled DNA with palindromic sequence, indicating that it may promote strand exchange reactions in homologous recombination. RuvAB is a helicase that mediates the Holliday junction migration by localized denaturation and reannealing. Participates in UV-tolerance of Synechocystis PCC 6803. ATP + H2O = ADP + H(+) + phosphate Forms a complex with RuvA. 2-3 fold induced by UV light. No visible phenotype; cells are more sensitive to UV-C light, H(2)O(2), CdSO(4), SeO(3) and SeO(4). This bacterium is considerably more resistant to UV and gamma irradiation than E.coli; the E.coli-like SOS regulon model is not an appropriate model for DNA repair in this cyanobacterium. Belongs to the RuvB family.