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Lon-dependent proteolysis of CcdA is the key control for activation of CcdB in plasmid-free segregant bacteria

Authors

  • Laurence Van Melderen,

    Corresponding author
    1. Laboratoire de Génétique, Département de Biologie Moléculaire, Université Libre de Bruxelles, rue des Chevaux 67, B-1640 Rhode Saint Genèse, Belgium.
    • *For correspondence. Tel. (2) 6509752; Fax (2) 6509744.

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  • Philippe Bernard,

    1. Laboratoire de Génétique, Département de Biologie Moléculaire, Université Libre de Bruxelles, rue des Chevaux 67, B-1640 Rhode Saint Genèse, Belgium.
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  • Martine Couturier

    1. Laboratoire de Génétique, Département de Biologie Moléculaire, Université Libre de Bruxelles, rue des Chevaux 67, B-1640 Rhode Saint Genèse, Belgium.
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Summary

The ccd locus contributes to the stability of plasmid F by post-segregational killing of plasmid-free bacteria. The ccdB gene product is a potent cell-killing protein and its activity is negatively regulated by the CcdA protein, in this paper, we show that the CcdA protein is unstable and that the degradation of CcdA is dependent on the Lon protease. Differences in the stability of the killer CcdB protein and its antidote CcdA are the key to post-segregational killing. Because the half-life of active CcdA protein is shorter than that of active CcdB protein, persistence of the CcdB protein leads to the death of plasmid-free bacterial segregants.

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