Structural and Functional Characterization of the Type Three Secretion System (T3SS) Needle of .

Authors:
Charlotte Lombardi
Charlotte Lombardi
The Laboratoire de Virologie Moléculaire et Structurale
Luca Signor
Luca Signor
Université Grenoble Alpes
Grenoble | France
Caroline Gebus
Caroline Gebus
University College Dublin
Ireland
David Liebl
David Liebl
Charles University in Prague
Czech Republic
Daphna Fenel
Daphna Fenel
UMR 5086 CNRS Université de Lyon
France
Jean-Marie Teulon
Jean-Marie Teulon
Institute for Biotechnology and Environmental Biology
France

Front Microbiol 2019 29;10:573. Epub 2019 Mar 29.

Univ. Grenoble Alpes, CEA, CNRS, Institut de Biologie Structurale (IBS), Grenoble, France.

The type three secretion system (T3SS) is a macromolecular protein nano-syringe used by different bacterial pathogens to inject effectors into host cells. The extracellular part of the syringe is a needle-like filament formed by the polymerization of a 9-kDa protein whose structure and proper localization on the bacterial surface are key determinants for efficient toxin injection. Here, we combined , , and approaches to characterize the T3SS needle and its major component PscF. Using a combination of mutagenesis, phenotypic analyses, immunofluorescence, proteolysis, mass spectrometry, atomic force microscopy, electron microscopy, and molecular modeling, we propose a model of the needle that exposes the N-terminal region of each PscF monomer toward the outside of the filament, while the core of the fiber is formed by the C-terminal helix. Among mutations introduced into the needle protein PscF, D76A, and P47A/Q54A caused a defect in the assembly of the needle on the bacterial surface, although the double mutant was still cytotoxic on macrophages in a T3SS-dependent manner and formed filamentous structures in . These results suggest that the T3SS needle of displays an architecture that is similar to that of other bacterial needles studied to date and highlight the fact that small, targeted perturbations in needle assembly can inhibit T3SS function. Therefore, the T3SS needle represents an excellent drug target for small molecules acting as virulence blockers that could disrupt pathogenesis of a broad range of bacteria.

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Source
https://www.frontiersin.org/article/10.3389/fmicb.2019.00573
Publisher Site
http://dx.doi.org/10.3389/fmicb.2019.00573DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6455054PMC
March 2019
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