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Location of the site-specific recombination system of R46: a function necessary for plasmid maintenance
Abstract:
The R46 site-specific recombination system comprises a per (plasmid-encoded recombinase) gene and a site at which the gene product acts, the per site. The two functions have been cloned into pACYC184. They are encoded by sequences within a region of approximately 2 kb on the R46 genome. These R46 sequences are closely related to the site-specific recombination systems of the ampicillin resistance transposons collectively designated TnA. The R46 per function is interchangeable with the tnpR gene product of TnA. Both enzymes can mediate recombination between the related res and per sites in R46::TnA recombinant plasmids to generate site-specific deletions and inversions. Similar DNA rearrangements occur when TnA inserts into pACYC184 derivatives carrying the cloned R46 per functions. Carriage of this site-specific recombination system contributes to the stable maintenance of R46. By converting plasmid dimers to monomers the R46 per functions help to ensure equal partitioning at cell division.
Insights
The R46 site-specific recombination system, involving the per gene and per site, aids in stable plasmid maintenance. This system converts plasmid dimers to monomers, ensuring equal partitioning during cell division.
Area of Science:
- Molecular Biology
- Genetics
- Microbiology
Background:
- The R46 plasmid utilizes a site-specific recombination system for stable maintenance.
- This system involves a recombinase gene (per) and its target site (per site).
- R46 sequences are homologous to ampicillin resistance transposons (TnA).
Purpose of the Study:
- To clone and characterize the R46 site-specific recombination system.
- To investigate the functional interchangeability between R46 per and TnA tnpR.
- To understand the role of this system in plasmid stability and maintenance.
Main Methods:
- Cloning of R46 per gene and per site into pACYC184.
- Analysis of DNA rearrangements (deletions, inversions) mediated by R46 per and TnA tnpR.
- Experimental validation of enzyme interchangeability between related sites.
Main Results:
- The R46 per function and per site were cloned within a 2 kb region of the R46 genome.
- The R46 per function is interchangeable with the TnA tnpR gene product.
- Both enzymes mediate recombination between R46::TnA plasmids, causing deletions and inversions.
- Similar rearrangements occur when TnA inserts into plasmids carrying R46 per functions.
Conclusions:
- The R46 site-specific recombination system contributes to the stable maintenance of the R46 plasmid.
- The per functions ensure equal partitioning of plasmids by converting dimers to monomers during cell division.