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In situ and high-resolution Cryo-EM structure of the Type VI secretion membrane complex
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Article de revue
Este ítem está publicado en
EMBO Journal. 2019-05-15, vol. 38, n° 10
Resumen en inglés
Bacteria have evolved macromolecular machineries that secrete effectors and toxins to survive and thrive in diverse environments. The type VI secretion system (T6SS) is a contractile machine that is related to phages. It ...Leer más >
Bacteria have evolved macromolecular machineries that secrete effectors and toxins to survive and thrive in diverse environments. The type VI secretion system (T6SS) is a contractile machine that is related to phages. It is composed of a phage tail-like structure inserted in the bacterial cell envelope by a membrane complex (MC) comprising the TssJ, TssL and TssM proteins. We previously reported the low-resolution negative-stain electron microscopy structure of the enteroaggregative MC and proposed a rotational 5-fold symmetry with a TssJ:TssL:TssM stoichiometry of 2:2:2. Here, cryo-electron tomography analyses of the T6SS MC confirm the 5-fold symmetry and identify the regions of the structure that insert into the bacterial membranes. A high-resolution model obtained by single-particle cryo-electron microscopy highlights new features: five additional copies of TssJ, yielding a TssJ:TssL:TssM stoichiometry of 3:2:2, an 11-residue loop in TssM, protruding inside the lumen of the MC and constituting a functionally important periplasmic gate, and hinge regions. Based on these data, we propose an updated model on MC structure and dynamics during T6SS assembly and function.< Leer menos
Palabras clave en inglés
Bacterial Secretion Systems
Cell Membrane
Cryoelectron Microscopy
Escherichia coli
Escherichia coli Proteins
Membrane Proteins
Models
Molecular
Protein Binding
Protein Structure
Quaternary
Type VI Secretion Systems
Centros de investigación