Lambda phage

About: Lambda phage is a research topic. Over the lifetime, 1609 publications have been published within this topic receiving 84675 citations. The topic is also known as: Enterobacteria phage lambda.

Cloning and mapping of a gene for translational initiation factor IF2 in Escherichia coli.

Abstract: A novel method, not relying on genetic complementation of a mutation, was used to clone a gene for translational initiation factor IF2. Two clones from a cosmid library of total Escherichia coli DNA were isolated for their ability to overproduce IF2 in vivo as determined by quantitative immunoblotting. "Maxicell" analysis of cosmid-encoded proteins and specific immune precipitation of the labeled proteins showed that the structural gene for IF2 (inf B) had been cloned. Subcloning fragments from the original cosmids located the inf B gene to a 4.8-kilobase pair HindIII/BamHI fragment. This fragment has been inserted into an integration-deficient recombinant lambda phage that lysogenizes by homology. By mapping the point of lysogenization on the E. coli chromosome, inf B has been located at 68 min, very close to argG, nusA, rpsO, and pnp. Because the gene for initiation factor IF3 is located at 38 min on the chromosome, the genes for translational initiation factors are not grouped together.

Molecular cloning of four tricarboxylic acid cyclic genes of Escherichia coli

Abstract: A fragment of DNA (3.1 kilobases [kb]) from a ColE1 Escherichia coli DNA hybrid plasmid containing the bacterial citrate synthase gene (gltA) was subcloned in both orientations into phage lambda vectors by in vitro recombination. The resulting phages were able to transduce gltA and, as prophages, complemented the lesion of a gltA mutant, showing that a functional gltA gene is contained in the 3.1-kb fragment. The segment of E. coli DNA cloned in these lambda gltA phages was extended in vivo by prophage integration and aberrant excision in the gltA region. Plaque-forming derivatives, carrying up to three additional tricarboxylic acid cycle genes, succinate dehydrogenase (sdh), 2-oxoglutarate dehydrogenase (sucA), and dihydrolipoamide succinyltransferase (sucB), were isolated and characterized by their transducing and complementing activities with corresponding mutants, and the order of the genes was confirmed as gltA-sdh-sucA-sucB. Physical maps of a variety of the transducing phages showed that the four tricarboxylic acid cycle genes are contained in a 12.8-kb segment of bacterial DNA. The four gene products, plus a possible succinate dehydrogenase small subunit, were identified in postinfection labeling studies, and the polarities of gene expression were defined as counterclockwise for gltA and clockwise for sdh, sucA, and sucB, relative to the E. coli linkage map.

On the Role of recA Gene Product in Genetic Recombination: An Analysis by in vitro Packaging of Recombinant DNA Molecules Formed in the Absence of Protein Synthesis

Abstract: The role of the recA gene product of Escherichia coli in genetic recombination was examined in a system where recombination takes place in the absence of protein synthesis. recA200 bacteria were infected with two mutant strains of phage lambda in the presence of chloramphenicol and rifampin, and the resulting recombinant DNA molecules were measured by in vitro packaging. When recA200 bacteria grown at a temperature that is permissive for RecA phenotype were transferred to a temperature that is restrictive for RecAa phenotype in the presence of the inhibitors, recombination of the infecting phages was severely blocked. This result shows that the recombination activity of the recA200 cells is inactivated by the change of temperature even in the absence of protein synthesis. The most likely explanation of this result is that the recA protein is directly involved in the recombination detected in the presence of chloramphenicol and rifampin.

[15] Purification and properties of the bacteriophage lambda int protein

Abstract: Publisher Summary In living systems, recombinant DNA is often formed by a crossover between specific sequences on DNA. The integration of bacteriophage lambda DNA into the chromosome of Escherichia coli is a particularly well-studied example of such site-specific recombination. Cell-free extracts carry out integrative recombination between the specialized recombining site of the phage, attP, and that of the bacterium, attB. In vitro recombination provides a functional assay for the components involved in the integration of phage lambda DNA. This approach has led to the discovery of two proteins that are encoded by the E. coli host: DNA gyrase and integration host factor (IHF). The role of DNA gyrase in integrative recombination is simply to provide a suitably supercoiled substrate DNA. Recombination of supercoiled DNA requires only IHF and a viral protein, Int, the product of the phage int gene. Recent studies indicate that Int carries the active site responsible for the breakage and reunion of DNA at the crossover; IHF plays an important but secondary role. This chapter describes the purification of Int and discusses the properties of the purified protein. A model is also prepared that suggests how a crossover can be carried out by a topoisomerase.

Transcription antitermination by phage lambda gene Q protein requires a DNA segment spanning the RNA start site.

Abstract: The gene Q protein of phage lambda is a transcription antiterminator that modifies RNA polymerase near the phage late gene promoter and thereby causes antitermination at distant sites. To define the site of action of Q protein, we have reconstructed the regulatory system on plasmids that allow the intracellular concentration of Q protein to be regulated, and that allow the effect of Q protein on transcription from variant promoter segments to be measured in vivo and in vitro. We show that DNA sequences essential for Q protein-mediated antitermination span the RNA start site, but do not extend beyond nucleotide 18 of the late RNA coding region. We also show that the modification that permits antitermination persists while RNA polymerase passes at least two terminators in vivo and in vitro.