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Nature. 2016 Mar 3;531(7592):59-63. doi: 10.1038/nature17182. Epub 2016 Feb 24.

Priming and polymerization of a bacterial contractile tail structure.

Author information

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.
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.
3
Architecture et Fonction des Macromolécules Biologiques, Aix-Marseille Université, UMR 7257, Campus de Luminy, Case 932, 13288 Marseille Cedex 09, France.
4
G5 Biologie structurale de la sécrétion bactérienne, Institut Pasteur, 25-28 rue du Docteur Roux, 75015 Paris, France.
5
UMR 3528, CNRS, Institut Pasteur, 25-28 rue du Docteur Roux, 75015 Paris, France.
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.
7
Synchrotron Soleil, L'Orme des merisiers, Saint-Aubin BP48, 91192 Gif-sur-Yvette Cedex, France.

Abstract

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.

PMID:
26909579
DOI:
10.1038/nature17182
[Indexed for MEDLINE]

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