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 an helicase that mediates the Holliday junction migration by localized denaturation and reannealing. RuvB is a Mg(2+)-dependent, DNA-dependent ATPase with an equal preference for supercoiled and linear duplex DNA. It can promote Holliday junction migration alone.