Site-specific tyrosine recombinase, which acts by catalyzing the cutting and rejoining of the recombining DNA molecules. Although strongly related to the XerC and XerD proteins, it lacks the Tyr active site, as well as the Arg-His-Arg-His (R-H-R-H) sandwich residues that are clustered with it. It however contains the Thr-Arg-Gln tripeptide, which is characteristic of the XerD subfamily. Belongs to the 'phage' integrase family.