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. Belongs to the RuvB family.