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Priming and polymerization of a bacterial contractile tail structure

Nature volume 531, pages 5963 (03 March 2016) | Download Citation


Contractile tails are composed of an inner tube wrapped by an outer sheath assembled in an extended, metastable conformation that stores mechanical energy necessary for its contraction. Contraction is used to propel the rigid inner tube towards target cells for DNA or toxin delivery. Although recent studies have revealed the structure of the contractile sheath of the type VI secretion system, the mechanisms by which its polymerization is controlled and coordinated with the assembly of the inner tube remain unknown. Here we show that the starfish-like TssA dodecameric complex interacts with tube and sheath components. Fluorescence microscopy experiments in enteroaggregative Escherichia coli reveal that TssA binds first to the type VI secretion system membrane core complex and then initiates tail polymerization. TssA remains at the tip of the growing structure and incorporates new tube and sheath blocks. On the basis of these results, we propose that TssA primes and coordinates tail tube and sheath biogenesis.

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Electron Microscopy Data Bank

Data deposits

Coordinates and structure factors have been deposited in the Protein Data Bank under accession numbers 4YO3 and 4YO5 for TssANt2 and TssACt respectively. Electron microscopy map for full-length TssA has been deposited in the Electron Microscopy Data Bank under accession code EMD-3282.


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This work was funded by the Centre National de la Recherche Scientifique, the Aix-Marseille Université, and grants from the Agence Nationale de la Recherche to E.C. (ANR-10-JCJC-1303-03), to E.C. and C.C. (ANR-14-CE14-0006-02) and from the Fondation pour la Recherche Médicale to C.C. (FRM DEQ2011-0421282) and supported by the French Infrastructure for Integrated Structural Biology (FRISBI, ANR-10-INSB-05-01). A.Z. and Y.R.B. were supported by doctoral fellowships from the French Ministry of Research. A.Z. and E.D. were supported by end-of-thesis (FDT20140931060) and post-doctoral (SPF20101221116) fellowships from the Fondation pour la Recherche Médicale, respectively. We gratefully acknowledge the Soleil synchrotron radiation facility for beamtime allocation. We thank R. Lloubès, J. Sturgis and A. Galinier for constant support, the members of the Cascales, Cambillau, Lloubès, Sturgis and Bouveret research groups for helpful discussions, E. Bouveret for providing vectors, protocols and advice for the bacterial two-hybrid assay, C. Bebeacua for preliminary electron microscopy analyses, L. Espinosa for help regarding statistical analyses, R. Lebrun and S. Lignon (proteomic platform, IMM) for mass spectrometry analyses, Y. Cully for the Supplementary Video, O. Uderso, I. Bringer and A. Brun for technical assistance, and J. D. Barras-Elatable for encouragement.

Author information

Author notes

    • Yannick R. Brunet

    Present address: Department of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, Massachussets 02115, USA.

    • Abdelrahim Zoued
    •  & Eric Durand

    These authors contributed equally to this work.


  1. Laboratoire d’Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, CNRS UMR7255, Aix-Marseille Université, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France

    • Abdelrahim Zoued
    • , Eric Durand
    • , Yannick R. Brunet
    • , Badreddine Douzi
    • , Nicolas Flaugnatti
    • , Laure Journet
    •  & Eric Cascales
  2. Architecture et Fonction des Macromolécules Biologiques, Centre National de la Recherche Scientifique, UMR 7257, Campus de Luminy, Case 932, 13288 Marseille Cedex 09, France

    • Eric Durand
    • , Silvia Spinelli
    • , Badreddine Douzi
    •  & Christian Cambillau
  3. Architecture et Fonction des Macromolécules Biologiques, Aix-Marseille Université, UMR 7257, Campus de Luminy, Case 932, 13288 Marseille Cedex 09, France

    • Eric Durand
    • , Silvia Spinelli
    • , Badreddine Douzi
    •  & Christian Cambillau
  4. G5 Biologie structurale de la sécrétion bactérienne, Institut Pasteur, 25–28 rue du Docteur Roux, 75015 Paris, France

    • Eric Durand
    •  & Rémi Fronzes
  5. UMR 3528, CNRS, Institut Pasteur, 25–28 rue du Docteur Roux, 75015 Paris, France

    • Eric Durand
    •  & Rémi Fronzes
  6. Laboratoire de Chimie Bactérienne, Institut de Microbiologie de la Méditerranée, CNRS UMR7283, Aix-Marseille Université, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France

    • Mathilde Guzzo
    •  & Tâm Mignot
  7. Synchrotron Soleil, L’Orme des merisiers, Saint-Aubin BP48, 91192 Gif-sur-Yvette Cedex, France

    • Pierre Legrand


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A.Z., E.D., C.C. and E.C. designed and conceived the experiments. C.C. and E.C supervised the execution of the experiments. A.Z., E.D., Y.R.B., S.S., B.D. and M.G. performed the experiments. A.Z. performed the in vivo experiments (BACTH, fluorescence microscopy) with the help of Y.R.B., M.G., N.F., L.J. and T.M. E.D. performed the in vitro experiments (protein purification and characterization, SAXS, electron microscopy and X-ray analyses) with the help of S.S., P.L. and R.F. B.D. performed the SPR experiments. P.L., R.F., T.M., C.C. and E.C. provided tools. E.C. wrote the paper with contributions of A.Z., E.D. and C.C.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Eric Durand or Christian Cambillau or Eric Cascales.

Extended data

Supplementary information

PDF files

  1. 1.

    Supplementary Table

    This file shows the strains, plasmids and oligonucleotides used in this study.

  2. 2.

    Supplementary Figure

    Uncropped scans of western blots and gels presented in Extended Data Fig. 1d, 1e, 2a & 6a. Molecular weight markers (in kDa) are indicated.


  1. 1.

    Dynamic representation of T6SS assembly highlighting the TssA mode of action

    The TssA protein (red ring) bound to the membrane and baseplate complexes (TssJLM shown in yellow/orange; VgrG spike, purple; baseplate, orange) initiates tail polymerization. Polymerization is pursued by the TssA-dependent sequential and processive recruitement of Hcp rings (green rings) and TssBC strands (blue rings). Once assembled, the sheath contracts and propels the Hcp/VgrG needle to the cell exterior.

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