Priming and polymerization of a bacterial contractile tail structure. 1' 2' 17'

Zoued, Abdelrahim Durand, Eric Brunet, Yannick R Spinelli, Silvia Douzi, Badreddine Guzzo, Mathilde Flaugnatti, Nicolas Legrand, Pierre Journet, Laure Fronzes, Remi Mignot, Tam Cambillau, Christian Cascales, Eric eng Research Support, Non-U.S. Gov't England Nature. 2016 Mar 3;531(7592):59-63. doi:10.1038/nature17182. Epub 2016 Feb 24. ; International audience ; 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 Type VI secretion system contractile sheath, the mechanisms by which its polymerization is controlled and coordinated with inner tube assembly remain unsolved. In this study, we report that the starfish-like TssA dodecameric complex interacts with tube and sheath components. Fluorescence microscopy experiments revealed that TssA binds first to the T6SS membrane core complex and then initiates tail polymerization. TssA remains at the tip of the growing structure and incorporates new tube and sheath blocks. Based on these results, we propose that TssA primes and coordinates tail tube and sheath biogenesis.