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Region of the streptococcal plasmid pMV158 required for conjugative mobilization
1Biology Department, Brookhaven National Laboratory, Upton, New York 11973.
Abstract:
The nonconjugative streptococcal plasmid pMV158 can be mobilized by the conjugative streptococcal plasmid pIP501. We determined the sequence of the 1.1-kilobase EcoRI fragment of pMV158 to complete the DNA sequence of the plasmid. We showed that an open reading frame, mob (able to encode a polypeptide of 58,020 daltons), is required for mobilization of pMV158. An intergenic region present in the EcoRI fragment contains four lengthy palindromes that are found also in one or more of the staphylococcal plasmids pT181, pE194, and pUB110. One palindromic sequence, palD, which is common to all four plasmids, also appeared to be necessary for mobilization. Circumstantial evidence indicates that this sequence contains both an oriT site and the mob promoter. The Mob protein is homologous in its amino-terminal half to Pre proteins encoded by pT181 and pE194 that were shown by others to be essential for site-specific cointegrative plasmid recombination; their main biological function may be plasmid mobilization.
Insights
The Mob protein, essential for streptococcal plasmid pMV158 mobilization, is encoded by a newly sequenced gene. This protein and a specific DNA sequence (palD) are crucial for the plasmid
Area of Science:
- Molecular Biology
- Microbiology
- Genetics
Background:
- Nonconjugative plasmids require mobilization by conjugative plasmids for transfer.
- Streptococcal plasmids like pMV158 are important genetic elements.
- Understanding plasmid mobilization mechanisms is key to genetic engineering.
Purpose of the Study:
- To complete the DNA sequencing of the nonconjugative streptococcal plasmid pMV158.
- To identify and characterize the genetic elements responsible for pMV158 mobilization.
- To elucidate the role of specific DNA sequences and proteins in plasmid mobilization.
Main Methods:
- DNA sequencing of the 1.1-kilobase EcoRI fragment of pMV158.
- Identification and analysis of open reading frames and intergenic regions.
- Sequence comparison with related staphylococcal plasmids (pT181, pE194, pUB110).
Main Results:
- The complete DNA sequence of pMV158 was determined.
- An open reading frame, mob, encoding a 58,020-dalton polypeptide, was identified and shown to be essential for mobilization.
- A common palindromic sequence, palD, was found to be necessary for mobilization and likely contains the origin of transfer (oriT) and mob promoter.
Conclusions:
- The Mob protein is essential for the mobilization of streptococcal plasmid pMV158.
- The palD sequence plays a critical role in mobilization, potentially acting as the oriT and mob promoter.
- The Mob protein shares homology with proteins involved in plasmid recombination, suggesting a conserved function in plasmid mobilization.