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Analysis of the transfer region of the Streptomyces plasmid SCP2
D F Brolle1, H Pape, D A Hopwood
1John Innes Institute, John Innes Centre, Norwich, UK.
Abstract:
pIJ903, a bifunctional derivative of the 31.4 kb low-copy-number, conjugative Streptomyces plasmid SCP2*, was mutagenized in Streptomyces lividans using Tn4560. Mutant plasmids differing in their transfer frequencies, chromosome mobilization abilities, pock formation, and complementation properties were isolated. The mutations defined five transfer-related genes, traA, traB, traC, traD and spd, clustered in a region of 9 kb. The deduced sequences of the putative TraA and TraB proteins showed no overall similarity to known protein sequences, but the phenotype of traA mutant plasmids and sequence motifs in the putative TraA protein suggested that it might be a DNA helicase.
Insights
Mutagenesis of the Streptomyces plasmid pIJ903 identified five new transfer genes. These genes are crucial for plasmid transfer and chromosome mobilization, with TraA potentially functioning as a DNA helicase.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- The Streptomyces plasmid SCP2* derivative, pIJ903, is a low-copy-number, conjugative plasmid.
- Understanding plasmid transfer mechanisms is essential for genetic manipulation of Streptomyces species.
Purpose of the Study:
- To identify and characterize genes involved in the conjugative transfer of the Streptomyces plasmid pIJ903.
- To investigate the function of these transfer genes in plasmid replication and chromosome mobilization.
Main Methods:
- Mutagenesis of pIJ903 using the transposon Tn4560 in Streptomyces lividans.
- Isolation and characterization of mutant plasmids with altered transfer frequencies and phenotypes.
- Sequence analysis of identified transfer genes.
Main Results:
- Five transfer-related genes (traA, traB, traC, traD, spd) were identified within a 9 kb cluster on pIJ903.
- Mutations in these genes affected plasmid transfer, chromosome mobilization, and pock formation.
- Putative TraA and TraB proteins showed no similarity to known sequences; TraA possesses motifs suggesting DNA helicase activity.
Conclusions:
- The identified gene cluster is essential for the conjugative transfer of pIJ903.
- The TraA protein is a potential DNA helicase involved in plasmid transfer.
- Further studies are needed to elucidate the precise functions of the identified genes and proteins.