A structure-specific endonuclease that resolves Holliday junction (HJ) intermediates during genetic recombination. Cleaves 4-way DNA junctions introducing paired nicks in opposing strands, leaving a 5'-terminal phosphate and a 3'-terminal hydroxyl group that are ligated to produce recombinant products. Cleaves both mobile and immobile junctions. Converts a synthetic Hj to nicked duplex products. Binds a variety of branched DNA structures but linear dsDNA poorly; cleaves only 4-way junctions. Confers UV and mitomycin C resistance to E.coli cells lacking the endogenous Hj machinery RuvABC. 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. Optimum pH is 7.8-9.5. Optimum temperature is 55 degrees Celsius. Homodimer. Belongs to the Holliday junction resolvase Hjc family.