title: Cooperative interactions between bacteriophage P2 integrase and its accessory factors IHF and Cox.
abstract: Bacteriophage P2 integrase (Int) mediates site-specific recombination leading to integration or excision of the phage genome in or out of the bacterial chromosome. Int belongs to the large family of tyrosine recombinases that have two different DNA recognition motifs binding to the arm and core sites, respectively, which are located within the phage attachment sites (attP). In addition to the P2 integrase, the accessory proteins Escherichia coli IHF and P2 Cox are needed for recombination. IHF is a structural protein needed for integration and excision by bending the DNA. As opposed to lambda, only one IHF site is found in P2 attP. P2 Cox controls the direction of recombination by inhibiting integration but being required for excision. In this work, the effects of accessory proteins on the capacity of Int to bind to its DNA recognition sequences are analyzed using electromobility shifts. P2 Int binds with low affinity to the arm site, and this binding is greatly enhanced by IHF. The arm binding domain of Int is located at the N-terminus. P2 Int binds with high affinity to the core site, and this binding is also enhanced by IHF. The fact that the cooperative binding of Int and IHF is strongly reduced by lengthening the distance between the IHF and core binding sites indicates that the distance between these sites may be important for cooperative binding. The Int and Cox proteins also bind cooperatively to attP.
authors.affiliation: Department of Genetics, Microbiology and Toxicology, Stockholm University, Svante Arrhenius väg 16, S-106 91 Stockholm, Sweden.
authors.forename: Clara
authors.initials: C
authors.lastname: Frumerie
authors.forename: Lina
authors.initials: L
authors.lastname: Sylwan
authors.forename: Alexandra
authors.initials: A
authors.lastname: Ahlgren-Berg
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Haggård-Ljungquist
mesh_terms: D017901:Bacteriophage P2 / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism / Q000821:virology*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D019426:Integrases / Q000378:metabolism*; D034982:Integration Host Factors / Q000378:metabolism*; D014764:Viral Proteins / Q000378:metabolism*; D016662:Virus Integration
chemical_list: C070354:Cox protein, Enterobacteria phage P2; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D034982:Integration Host Factors; D014764:Viral Proteins; C440502:integration host factor, E coli; D019426:Integrases