title: Function of IHF in lambda DNA packaging. II. Effects of mutations altering the IHF binding site and the intrinsic bend in cosB on lambda development.
abstract: cosB is the binding site on lambda DNA for terminase, the phage DNA packaging protein. cosB contains three binding sites for gpNu1, the small subunit of terminase, and a site for integration host factor (IHF). IHF plays an accessory role in lambda DNA packaging, and IHF stimulates the burst size of lambda several-fold, presumably by assisting the interaction of terminase with cosB. The present work includes a study of the effect on lambda development of a mutation, called I1A-, which consists of three adjacent base-pair changes in the IHF binding site. The I1A- mutation was found to abolish IHF stimulation of the lambda burst size, indicating that IHF is unable to bind to the mutant I1A site. A second mutation, called I1B- and also consisting of three adjacent base-pair changes, is a mutation that reduces an intrinsic bend found in cosB. lambda I1B- was more dependent on IHF than lambda+, raising the possibility that the intrinsic bend in cosB plays a role in cos function for lambda+ under the IHF- conditions. In vitro DNA packaging experiments established that the I1 mutations affect DNA packaging per se. A series of Nu1 mutations that create terminases able to suppress a variety of cosB defects were found to suppress the defects of the I1A- and I1B- mutations under IHF- conditions.
authors: Genetics Ph.D. Program, University of Iowa, Iowa City 52242.
authors: W
authors: W
authors: Xin
authors: Z H
authors: ZH
authors: Cai
authors: M
authors: M
authors: Feiss
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D010582:Bacteriophage lambda / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D004279:DNA, Viral / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004706:Endodeoxyribonucleases / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D034982:Integration Host Factors; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides; D010641:Phenotype; D010957:Plasmids; D013489:Suppression, Genetic
chemical_list: D001426:Bacterial Proteins; D004279:DNA, Viral; D004268:DNA-Binding Proteins; D034982:Integration Host Factors; D009838:Oligodeoxyribonucleotides; D004706:Endodeoxyribonucleases; C030894:terminase