Has at least 2 separable functions; Holliday junction resolution with generation of monomeric chromosomes, and modulation of RecA activity. Endonuclease that resolves Holliday junction intermediates in genetic recombination. Cleaves mobile four-strand junctions by introducing symmetrical nicks in paired strands. Promotes annealing of linear ssDNA with homologous dsDNA. Required for DNA repair, homologous recombination and chromosome segregation. Partially inhibits the hydrolysis of dATP or rATP by RecA. Holliday junction resolution is stimulated by RuvB. Endonucleolytic cleavage at a junction such as a reciprocal single-stranded crossover between two homologous DNA duplexes (Holliday junction). Binds 1 Mg(2+) ion per subunit. Homodimer. Interacts with RuvB. Cells lacking this gene have a greatly increased sensitivity to DNA damaging agents, 25-fold decreased plasmid transformation and only slightly reduced chromosomal DNA transformation (PubMed:10692371). They form anucleate cells 100-times more frequently than wild-type cells during normal growth (PubMed:18684995). DNA damaging agent sensitivity is partially suppressed by disruption of radA and fin (also called sms and subA respectively) (PubMed:11810266). Belongs to the RecU family. Recombination protein U, a short form proposed to initiate from Met-33, which is equivalent to RecU-delta1-32, is not detected in vivo, and would not be functional. The name is misleading and should no longer be used. Was originally named prfA (Penicillin-binding protein-related factor A, PBP-related factor A) due to its proximity to the ponA gene; this name is misleading and should no longer be used.