Dimerization of bacteriophage P2 integrase is not required for binding to its DNA target but for its biological activity.

Coliphage P2 integrates into the host chromosome upon lysogenization via site-specific recombination mediated by the phage integrase (Int). P2 integrase belongs to the tyrosine family of recombinases. In this work, it is shown that P2 integrase forms dimers but not oligomers in the absence of its DNA target. Furthermore, the C-terminal end of the protein and amino acid (aa) E197 have been found to be involved in dimerization. Amino acid E197 is located in a conserved region of the tyrosine recombinases that has not previously been implicated in dimerization. The dimerization deficient mutants were unaffected in binding to its phage attachment site (attP) substrate, but had a reduced ability to complement an int-defective prophage.