Bacteriophage lambda integrase (Int) catalyzes the integration and excision of the phage lambda chromosome into and out of the Esherichia coli host chromosome. The seven carboxy-terminal residues (C-terminal tail) of Int comprise a context-sensitive regulatory element that links catalytic function with protein multimerization and also coordinates Int functions within the multimeric recombinogenic complex. The experiments reported here show that the beta5-strand of Int is not simply a placeholder for the C-terminal tail but rather exerts its own allosteric effects on Int function in response to the incoming tail. Using a mutant integrase in which the C-terminal tail has been deleted (W350ter), we demonstrate that the C-terminal tail is required for efficient and accurate resolution of Holliday junctions by tetrameric Int. Addition of a free heptameric peptide of the same sequence as the C-terminal tail partially reverses the W350ter defects by stimulating Holliday junction resolution. The peptide also stimulates the topoisomerase function of monomeric W350ter. Single residue alterations in the peptide sequence and a mutant of the beta5 strand indicate that the observed stimulation arises from specific contacts with the beta5 strand (residues 239-243). The peptide does not stimulate binding of W350ter to its cognate DNA sites and therefore appears to recapitulate the effects of the normal C-terminal tail intermolecular contacts in wild-type Int. Models for the allosteric stimulation of Int activity by beta5 strand contacts are discussed.
Receipt of the C-terminal tail from a neighboring lambda Int protomer allosterically stimulates Holliday junction resolution
Hazelbaker, D.; Radman-Livaja, M.; Landy, A.
Journal of molecular biology
2005-09-02 / vol 351 / pages 948-55
0022-2836 (Print) 0022-2836 (Linking)
IGMM team(s) involved in this publication
Chromatin and DNA replication
Models, Molecular; Protein Binding; Models, Genetic; Protein Conformation; Time Factors; Nucleic Acid Conformation; *Recombination, Genetic; Crystallography, X-Ray; Protein Structure, Tertiary; Dose-Response Relationship, Drug; Bacteriophage lambda/*enzymology/genetics; Allosteric Site; Chromosomes, Bacterial/metabolism; DNA, Cruciform; DNA/chemistry; Escherichia coli/metabolism; Integrases/*chemistry/*genetics; Molecular Conformation; Peptides/chemistry; Proteins/chemistry