A comparative analysis of the bifunctional Cox proteins of two heteroimmune P2-like phages with different host integration sites.

The Cox protein of the coliphage P2 is multifunctional; it acts as a transcriptional repressor of the Pc promoter, as a transcriptional activator of the P(LL) promoter of satellite phage P4, and as a directionality factor for site-specific recombination. The Cox proteins constitute a unique group of directionality factors since they couple the developmental switch with the integration or excision of the phage genome. In this work, the DNA binding characteristics of the Cox protein of WPhi, a P2-related phage, are compared with those of P2 Cox.

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.