Conclusion:

As shown, the Cre recombinase/loxP system in bacteriophage catalyzes recombination through the use of stepwise cleaving to form a Holliday Junction Intermediate, isomerization, to another Holliday Junction Intermediate, and cleavage to complete the strand exchange. The Cre recombinase enzyme is a tetramer composed of identical subunits all having a catalytic domain that bind to one half of the loxP site cooperatively forming a dimer. The dimers tetramerize to bend the DNA to allow for recmbination. The protein/DNA interactions were shown to the latest data but the whole picture has not been fully developed yet and is still being researched.