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Structural and mechanistic insights into the bacterial amyloid secretion channel CsgG

Goyal, P; Krasteva, PV; Van Gerven, N; Gubellini, F; Van den Broeck, I; Troupiotis-Tsaïlaki, A; Jonckheere, W; ... Remaut, H; + view all (2014) Structural and mechanistic insights into the bacterial amyloid secretion channel CsgG. [Letter]. Nature , 516 pp. 250-253. 10.1038/nature13768. Green open access

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Abstract

Curli are functional amyloid fibres that constitute the major protein component of the extracellular matrix in pellicle biofilms formed by Bacteroidetes and Proteobacteria (predominantly of the α and γ classes). They provide a fitness advantage in pathogenic strains and induce a strong pro-inflammatory response during bacteraemia. Curli formation requires a dedicated protein secretion machinery comprising the outer membrane lipoprotein CsgG and two soluble accessory proteins, CsgE and CsgF. Here we report the X-ray structure of Escherichia coli CsgG in a non-lipidated, soluble form as well as in its native membrane-extracted conformation. CsgG forms an oligomeric transport complex composed of nine anticodon-binding-domain-like units that give rise to a 36-stranded β-barrel that traverses the bilayer and is connected to a cage-like vestibule in the periplasm. The transmembrane and periplasmic domains are separated by a 0.9-nm channel constriction composed of three stacked concentric phenylalanine, asparagine and tyrosine rings that may guide the extended polypeptide substrate through the secretion pore. The specificity factor CsgE forms a nonameric adaptor that binds and closes off the periplasmic face of the secretion channel, creating a 24,000 Å(3) pre-constriction chamber. Our structural, functional and electrophysiological analyses imply that CsgG is an ungated, non-selective protein secretion channel that is expected to employ a diffusion-based, entropy-driven transport mechanism.

Type: Article
Title: Structural and mechanistic insights into the bacterial amyloid secretion channel CsgG
Open access status: An open access version is available from UCL Discovery
DOI: 10.1038/nature13768
Publisher version: http://dx.doi.org/10.1038/nature13768
Language: English
Additional information: Copyright © 2014 Macmillan Publishers Limited. All rights reserved.
Keywords: X-ray crystallography, Bacterial secretion, Lipoproteins, Nanopores
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
URI: https://discovery.ucl.ac.uk/id/eprint/1449023
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