The bacteriophage λ site-specific recombinase (Int), in contrast to other family members such as Cre and Flp, has an amino-terminal domain that binds "arm-type" DNA sequences different and distant from those involved in strand exchange. This defining feature of the heterobivalent recombinases confers a directionality and regulation that is unique among all recombination pathways. We show that the amino-terminal domain is not a simple "accessory" element, as originally thought, but rather is incorporated into the core of the recombination mechanism, where it is well positioned to exert its profound effects. The results reveal an unexpected pattern of intermolecular interactions between the amino-terminal domain of one protomer and the linker region of its neighbor within the tetrameric Int complex and provide insights into those features distinguishing an "active" from an "inactive" pair of Ints during Holliday junction resolution.
Bibliographical noteFunding Information:
We thank Christine Lank for technical assistance, Joan Boyles for manuscript preparation, and members of the Landy and Ellenberger laboratories for helpful discussions. This work was supported by National Institutes of Health grants GM62723 and GM33928 to A.L. and GM59902 to T.E.
- E. coli bacteriophage
- multimeric complexes
- protein-DNA interactions
- protein-protein interactions
- site-specific recombination