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TraG from RP4 and TraG and VirD4 from Ti Plasmids Confer Relaxosome Specificity to the Conjugal Transfer System of pTiC58
- Source :
- Journal of Bacteriology. 182:1541-1548
- Publication Year :
- 2000
- Publisher :
- American Society for Microbiology, 2000.
-
Abstract
- Plasmid conjugation systems are composed of two components, the DNA transfer and replication system, or Dtr, and the mating pair formation system, or Mpf. During conjugal transfer an essential factor, called the coupling protein, is thought to interface the Dtr, in the form of the relaxosome, with the Mpf, in the form of the mating bridge. These proteins, such as TraG from the IncP1 plasmid RP4 (TraG RP4 ) and TraG and VirD4 from the conjugal transfer and T-DNA transfer systems of Ti plasmids, are believed to dictate specificity of the interactions that can occur between different Dtr and Mpf components. The Ti plasmids of Agrobacterium tumefaciens do not mobilize vectors containing the oriT of RP4, but these IncP1 plasmid derivatives lack the trans -acting Dtr functions and TraG RP4 . A. tumefaciens donors transferred a chimeric plasmid that contains the oriT and Dtr genes of RP4 and the Mpf genes of pTiC58, indicating that the Ti plasmid mating bridge can interact with the RP4 relaxosome. However, the Ti plasmid did not mobilize transfer from an IncQ relaxosome. The Ti plasmid did mobilize such plasmids if TraG RP4 was expressed in the donors. Mutations in traG RP4 with defined effects on the RP4 transfer system exhibited similar phenotypes for Ti plasmid-mediated mobilization of the IncQ vector. When provided with VirD4, the tra system of pTiC58 mobilized plasmids from the IncQ relaxosome. However, neither TraG RP4 nor VirD4 restored transfer to a traG mutant of the Ti plasmid. VirD4 also failed to complement a traG RP4 mutant for transfer from the RP4 relaxosome or for RP4-mediated mobilization from the IncQ relaxosome. TraG RP4 -mediated mobilization of the IncQ plasmid by pTiC58 did not inhibit Ti plasmid transfer, suggesting that the relaxosomes of the two plasmids do not compete for the same mating bridge. We conclude that TraG RP4 and VirD4 couples the IncQ but not the Ti plasmid relaxosome to the Ti plasmid mating bridge. However, VirD4 cannot couple the IncP1 or the IncQ relaxosome to the RP4 mating bridge. These results support a model in which the coupling proteins specify the interactions between Dtr and Mpf components of mating systems.
- Subjects :
- Virulence Factors
Mutant
Genetics and Molecular Biology
Replication Origin
Biology
Microbiology
Ti plasmid
chemistry.chemical_compound
Plasmid
Bacterial Proteins
Escherichia coli
Molecular Biology
Gene
reproductive and urinary physiology
Genetics
Escherichia coli Proteins
DNA replication
Membrane Proteins
Agrobacterium tumefaciens
biochemical phenomena, metabolism, and nutrition
biology.organism_classification
Relaxosome
chemistry
Conjugation, Genetic
DNA
Plasmids
Subjects
Details
- ISSN :
- 10985530 and 00219193
- Volume :
- 182
- Database :
- OpenAIRE
- Journal :
- Journal of Bacteriology
- Accession number :
- edsair.doi.dedup.....89801b452d0eeaff59f92ab5b11c5124