Molecular and General Genetics MGG

, Volume 208, Issue 3, pp 365–372

Partitioning of the F plasmid: Overproduction of an essential protein for partition inhibits plasmid maintenance

  • Noriko Kusukawa
  • Hirotada Mori
  • Akihiro Kondo
  • Sota Hiraga
Article

DOI: 10.1007/BF00328125

Cite this article as:
Kusukawa, N., Mori, H., Kondo, A. et al. Mol Gen Genet (1987) 208: 365. doi:10.1007/BF00328125

Summary

Multicopy plasmids carrying the sopB gene of the F plasmid inhibit stable inheritance of a coexisting mini-F plasmid. This incompatibility, termed IncG, is found to be caused by excess amounts of the SopB protein, which is essential for accuratepartitioning of plasmid DNA molecules into daughter cells. A sopB-carrying multicopy plasmid that shows the IncG+ phenotype was mutagenized in vitro and IncG negative mutant plasmids were isolated. Among these amber and missense mutants of sopB, mutants with a low plasmid copy number and a mutant in the Shine-Dalgarno sequence for translation of the SopB protein were obtained. These results demonstrate that the IncG phenotype is caused by the SopB protein, and that the incompatibility is expressed only when the protein is overproduced. This suggests that the protein must be kept at appropriate concentrations to ensure stable maintenance of the plasmid.

Key words

Plasmid incompabibility Plasmid partition F plasmid DNA sequencing Plasmid stability 

Copyright information

© Springer-Verlag 1987

Authors and Affiliations

  • Noriko Kusukawa
    • 1
  • Hirotada Mori
    • 1
  • Akihiro Kondo
    • 2
  • Sota Hiraga
    • 1
  1. 1.Institute for Virus ResearchKyoto UniversityKyotoJapan
  2. 2.Central Research LaboratoriesTakara Shuzo Co. Ltd.Otsu, ShigaJapan
  3. 3.Department of Molecular Genetics, Institute for Medical GeneticsKumatoto University Medical SchoolKumamotoJapan