Protein-DNA complexes in mycobacteriophage L5 integrative recombination

The temperate mycobacteriophage L5 integrates site specifically into the ge nomes of Mycobacterium smegmatis, Mycobactrium tuberculosis, and Mycobacter ium bovis bacillus Calmette-Guerin. This integrative recombination event oc curs between the phage L5 attP site and the mycobacterial attB site and req uires the phage-encoded integrase and mycobacterial-encoded integration hos t factor mIHF, Here we show that attP, Int-L5, and mIHF assemble into a rec ombinationally active complex, the intasome, which is capable of attB captu re and formation of products. The arm-type integrase binding sites within a ttP play specialized roles in the formation of specific protein-DNA archite ctures; the intasome is constructed by the formation of intramolecular inte grase bridges between one pair of sites, P4-P5, and the attP core, while an additional pair of sites, P1-P2, is required for interaction with attB.