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Nat Microbiol. 2018 Dec;3(12):1404-1416. doi: 10.1038/s41564-018-0260-1. Epub 2018 Oct 15.

Biogenesis and structure of a type VI secretion baseplate.

Author information

1
Laboratoire d'Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, UMR7255, Aix-Marseille Université - CNRS, Marseille, France.
2
Institut Européen de Chimie et Biologie, University of Bordeaux, Pessac, France.
3
CNRS UMR 5234 Microbiologie Fondamentale et Pathogénicité, Paris, France.
4
Institut Pasteur, Structural Bioinformatics Unit, Department of Structural Biology and Chemistry, CNRS UMR 3528, C3BI USR 3756, Paris, France.
5
USR 2000, CNRS, Institut Pasteur, Paris, France.
6
Mass Spectrometry for Biology Unit, Institut Pasteur, Paris, France.
7
Institut Européen de Chimie et Biologie, University of Bordeaux, Pessac, France. r.fronzes@iecb.u-bordeaux.fr.
8
CNRS UMR 5234 Microbiologie Fondamentale et Pathogénicité, Paris, France. r.fronzes@iecb.u-bordeaux.fr.
9
Laboratoire d'Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, UMR7255, Aix-Marseille Université - CNRS, Marseille, France. eric.durand@inserm.fr.
10
Laboratoire d'Ingénierie des Systèmes Macromoléculaires , Institut de Microbiologie de la Méditerranée, UMR7255, INSERM, Marseille, France. eric.durand@inserm.fr.

Abstract

To support their growth in a competitive environment and cause pathogenesis, bacteria have evolved a broad repertoire of macromolecular machineries to deliver specific effectors and toxins. Among these multiprotein complexes, the type VI secretion system (T6SS) is a contractile nanomachine that targets both prokaryotic and eukaryotic cells. The T6SS comprises two functional subcomplexes: a bacteriophage-related tail structure anchored to the cell envelope by a membrane complex. As in other contractile injection systems, the tail is composed of an inner tube wrapped by a sheath and built on the baseplate. In the T6SS, the baseplate is not only the tail assembly platform, but also docks the tail to the membrane complex and hence serves as an evolutionary adaptor. Here we define the biogenesis pathway and report the cryo-electron microscopy (cryo-EM) structure of the wedge protein complex of the T6SS from enteroaggregative Escherichia coli (EAEC). Using an integrative approach, we unveil the molecular architecture of the whole T6SS baseplate and its interaction with the tail sheath, offering detailed insights into its biogenesis and function. We discuss architectural and mechanistic similarities but also reveal key differences with the T4 phage and Mu phage baseplates.

PMID:
30323254
DOI:
10.1038/s41564-018-0260-1

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