Molecular and General Genetics MGG

, Volume 226, Issue 1, pp 297–304

The 41 carboxy-terminal residues of the miniF plasmid CcdA protein are sufficient to antagonize the killer activity of the CcdB protein

  • Philippe Bernard
  • Martine Couturier

DOI: 10.1007/BF00273616

Cite this article as:
Bernard, P. & Couturier, M. Mol Gen Genet (1991) 226: 297. doi:10.1007/BF00273616


The ccd operon of plasmid F encodes two genes, ccdA and ccdB, which contribute to the high stability of the plasmid by post-segregational killing of plasmid-free bacteria. The CcdB protein is lethal to bacteria and the CcdA protein is an antagonist of this lethal action. A 520 by fragment containing the terminal part of the ccdA gene and the entire ccdB gene of plasmid F was cloned downstream of the tac promoter. Although the CcdB protein was expressed from this fragment, no killing of host bacteria was observed. We found that the absence of killing was due to the presence of a small polypeptide, CcdA41, composed of the 41 C-terminal residues of the CcdA protein. This polypeptide has retained the ability to regulate negatively the lethal activity of the CcdB protein.

Key words

F plasmidStability functionsccd mechanism

Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • Philippe Bernard
    • 1
  • Martine Couturier
    • 1
  1. 1.Laboratoire de Génétique, Département de Biologie MoléculaireUniversité libre de BruxellesRhode Saint GenèseBelgium