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Isolation and characterization of mutations in the bacteriophage lambda terminase genes
A Davidson1, P Yau, H Murialdo
1Department of Molecular and Medical Genetics, University of Toronto, Canada.
Journal of Bacteriology
|August 1, 1991
Summary
Researchers identified mutations in bacteriophage lambda terminase genes using a novel method. Some mutations affected the enzyme
Area of Science:
- Molecular Biology
- Virology
- Genetics
Background:
- Bacteriophage lambda terminase is a crucial hetero-oligomeric enzyme responsible for DNA cleavage and packaging into phage proheads.
- Terminase is composed of products from the lambda Nul and A genes.
- Understanding terminase function is vital for phage biology and genetic engineering applications.
Purpose of the Study:
- To develop a method for selecting mutations in lambda terminase genes.
- To analyze the impact of these mutations on terminase activity and DNA packaging.
- To identify regions within the terminase A gene, particularly the endonuclease domain.
Main Methods:
- A novel selection method was employed using the toxicity of wild-type terminase to recA strains of Escherichia coli.
- Sixty-three spontaneous and 13 linker insertion mutations in terminase genes were isolated and analyzed.
- In vitro lambda DNA packaging assays and genetic mapping using lambda Aam phages were performed.
Main Results:
- Mutant plasmids showed reduced activity of one or both terminase subunits in vitro.
- A gene mutations were distributed across the gene, with over half producing full-length A protein.
- Three mutants exhibited significantly reduced packaging of immature lambda DNA, suggesting roles in the endonuclease domain.
Conclusions:
- The study successfully developed a method to isolate and analyze terminase gene mutations.
- Specific mutations were identified that likely reside within the endonuclease domain of the terminase A gene.
- These findings provide insights into the structure-function relationships of bacteriophage lambda terminase.