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Cloning of bacterial DNA replication genes in bacteriophage lambda
Abstract:
Recombinant lambda phages containing the genes for dnaZ protein (the gamma subunit of DNA polymerse III holoenzyme), primase (dnaG protein) and dnaC protein from Escherichia coli and Salmonella typhimurium were isolated. Each gene cloned from S. typhimurium has extensive DNA sequence homology to the corresponding E. coli gene. Clones selected by complementation of a dnaA temperature-sensitive mutant appear similar to other isolated suppressors of dnaA (Projan and Wechsler 1981). Derivatives of each cloned fragment suitable for overproduction of the protein were constructed. Of those tested, only the phage containing the E. coli dnaZ gene resulted in significant overproduction.
Insights
Researchers isolated recombinant phages with genes for DNA polymerase III gamma subunit (dnaZ), primase (dnaG), and dnaC protein from E. coli and S. typhimurium. The E. coli dnaZ gene clone enabled significant protein overproduction.
Area of Science:
- Molecular Biology
- Bacteriology
Background:
- DNA replication is a fundamental process in bacteria, involving complex protein machinery.
- Understanding the genes encoding key replication proteins like dnaZ, dnaG, and dnaC is crucial for bacterial genetics.
Purpose of the Study:
- To isolate and characterize recombinant lambda phages carrying essential DNA replication genes from E. coli and S. typhimurium.
- To investigate the DNA sequence homology between homologous genes from these two bacterial species.
- To construct derivatives for protein overproduction and assess their expression levels.
Main Methods:
- Isolation of recombinant lambda phages containing dnaZ, dnaG, and dnaC genes.
- DNA sequence homology analysis between E. coli and S. typhimurium genes.
- Complementation assays using a dnaA temperature-sensitive mutant.
- Construction of expression vectors for protein overproduction.
Main Results:
- Recombinant phages carrying dnaZ, dnaG, and dnaC genes from both E. coli and S. typhimurium were successfully isolated.
- Extensive DNA sequence homology was observed between the cloned S. typhimurium and E. coli genes.
- Clones selected via complementation of a dnaA mutant showed similarities to known dnaA suppressors.
- Only the recombinant phage with the E. coli dnaZ gene demonstrated significant protein overproduction.
Conclusions:
- The study successfully cloned and characterized key DNA replication genes from E. coli and S. typhimurium.
- Homology suggests conserved mechanisms in DNA replication between these species.
- The E. coli dnaZ gene clone is a promising tool for overproducing the DNA polymerase III gamma subunit.