title: Identification of the lambda integrase surface that interacts with Xis reveals a residue that is also critical for Int dimer formation.
abstract: Lambda integrase (Int) is a heterobivalent DNA-binding protein that together with the accessory DNA-bending proteins IHF, Fis, and Xis, forms the higher-order protein-DNA complexes that execute integrative and excisive recombination at specific loci on the chromosomes of phage lambda and its Escherichia coli host. The large carboxyl-terminal domain of Int is responsible for binding to core-type DNA sites and catalysis of DNA cleavage and ligation reactions. The small amino-terminal domain (residues 1-70), which specifies binding to arm-type DNA sites distant from the regions of strand exchange, consists of a three-stranded beta-sheet, proposed to recognize the cognate DNA site, and an alpha-helix. We report here that a site on this alpha-helix is critical for both homomeric interactions between Int protomers and heteromeric interactions with Xis. The mutant E47A, which was identified by alanine-scanning mutagenesis, abolishes interactions between Int and Xis bound at adjacent binding sites and reduces interactions between Int protomers bound at adjacent arm-type sites. Concomitantly, this residue is essential for excisive recombination and contributes to the efficiency of the integrative reaction. NMR titration data with a peptide corresponding to Xis residues 57-69 strongly suggest that the carboxyl-terminal tail of Xis and the alpha-helix of the aminoterminal domain of Int comprise the primary interaction surface for these two proteins. The use of a common site on lambda Int for both homotypic and heterotypic interactions fits well with the complex regulatory patterns associated with this site-specific recombination reaction.
authors.affiliation: Division of Biology and Medicine, Brown University, Providence, RI 02912, USA.
authors.forename: David
authors.initials: D
authors.lastname: Warren
authors.forename: My D
authors.initials: MD
authors.lastname: Sam
authors.forename: Kate
authors.initials: K
authors.lastname: Manley
authors.forename: Dibyendu
authors.initials: D
authors.lastname: Sarkar
authors.forename: Sang Yeol
authors.initials: SY
authors.lastname: Lee
authors.forename: Mohamad
authors.initials: M
authors.lastname: Abbani
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Wojciak
authors.forename: Robert T
authors.initials: RT
authors.lastname: Clubb
authors.forename: Arthur
authors.initials: A
authors.lastname: Landy
mesh_terms: D010582:Bacteriophage lambda / Q000201:enzymology*; D001665:Binding Sites; D004247:DNA / Q000378:metabolism; D004254:DNA Nucleotidyltransferases / Q000737:chemistry* / Q000378:metabolism; D019281:Dimerization; D019426:Integrases / Q000737:chemistry* / Q000378:metabolism; D046911:Macromolecular Substances; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D014764:Viral Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D046911:Macromolecular Substances; D014764:Viral Proteins; D004247:DNA; D004254:DNA Nucleotidyltransferases; D019426:Integrases; C063911:excisionase