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Mounting, structure and autocleavage of a type VI secretion-associated Rhs polymorphic toxin

Abstract : Bacteria have evolved toxins to outcompete other bacteria or to hijack host cell pathways. One broad family of bacterial polymorphic toxins gathers multidomain proteins with a modular organization, comprising a C-terminal toxin domain fused to a N-terminal domain that adapts to the delivery apparatus. Polymorphic toxins include bacteriocins, contact-dependent growth inhibition systems, and specialized Hcp, VgrG, PAAR or Rhs Type VI secretion (T6SS) components. We recently described and characterized Tre23, a toxin domain fused to a T6SS-associated Rhs protein in Photorhabdus laumondii , Rhs1. Here, we show that Rhs1 forms a complex with the T6SS spike protein VgrG and the EagR chaperone. Using truncation derivatives and cross-linking mass spectrometry, we demonstrate that VgrG-EagR-Rhs1 complex formation requires the VgrG C-terminal β-helix and the Rhs1 N-terminal region. We then report the cryo-electron-microscopy structure of the Rhs1-EagR complex, demonstrating that the Rhs1 central region forms a β-barrel cage-like structure that encapsulates the C-terminal toxin domain, and provide evidence for processing of the Rhs1 protein through aspartyl autoproteolysis. We propose a model for Rhs1 loading on the T6SS, transport and delivery into the target cell.
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https://hal-amu.archives-ouvertes.fr/hal-03465940
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Submitted on : Tuesday, January 25, 2022 - 3:30:02 PM
Last modification on : Thursday, April 7, 2022 - 1:58:36 PM
Long-term archiving on: : Tuesday, April 26, 2022 - 6:58:38 PM

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Dukas Jurėnas, Leonardo Talachia Rosa, Martial Rey, Julia Chamot-Rooke, Rémi Fronzes, et al.. Mounting, structure and autocleavage of a type VI secretion-associated Rhs polymorphic toxin. Nature Communications, Nature Publishing Group, 2021, 12 (1), ⟨10.1038/s41467-021-27388-0⟩. ⟨hal-03465940⟩

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