Crystal structure of the excisionase-DNA complex from bacteriophage lambda.Sam, M.D., Cascio, D., Johnson, R.C., Clubb, R.T.
(2004) J.Mol.Biol. 338: 229-240
- PubMed: 15066428
- DOI: 10.1016/j.jmb.2004.02.053
- PubMed Abstract:
The excisionase (Xis) protein from bacteriophage lambda is the best characterized member of a large family of recombination directionality factors that control integrase-mediated DNA rearrangements. It triggers phage excision by cooperatively binding ...
The excisionase (Xis) protein from bacteriophage lambda is the best characterized member of a large family of recombination directionality factors that control integrase-mediated DNA rearrangements. It triggers phage excision by cooperatively binding to sites X1 and X2 within the phage, bending DNA significantly and recruiting the phage-encoded integrase (Int) protein to site P2. We have determined the co-crystal structure of Xis with its X2 DNA-binding site at 1.7A resolution. Xis forms a unique winged-helix motif that interacts with the major and minor grooves of its binding site using an alpha-helix and an ordered beta-hairpin (wing), respectively. Recognition is achieved through an elaborate water-mediated hydrogen-bonding network at the major groove interface, while the preformed hairpin forms largely non-specific interactions with the minor groove. The structure of the complex provides insights into how Xis recruits Int cooperatively, and suggests a plausible mechanism by which it may distort longer DNA fragments significantly. It reveals a surface on the protein that is likely to mediate Xis-Xis interactions required for its cooperative binding to DNA.
Department of Chemistry and Biochemistry and the UCLA-DOE Institute for Genomics and Proteomics, University of California, Los Angeles, 405 Hilgard Ave., Los Angeles, CA 90095-1570, USA.