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Characterisation of Shigella Spa33 and Thermotoga FliM/N reveals a new model for C-ring assembly in T3SS

Mcdowell, M.A.; Marcoux, J.; Mcvicker, G.; Johnson, S.; Fong, Y.H.; Stevens, R.; Bowman, L.A.H.; Degiacomi, M.T.; Yan, J.; Wise, A.; Friede, M.E.; Benesch, J.L.P.; Deane, J.E.; Tang, C.M.; Robinson, C.V.; Lea, S.M.

Characterisation of Shigella Spa33 and Thermotoga FliM/N reveals a new model for C-ring assembly in T3SS Thumbnail


Authors

M.A. Mcdowell

J. Marcoux

G. Mcvicker

S. Johnson

Y.H. Fong

R. Stevens

L.A.H. Bowman

J. Yan

A. Wise

M.E. Friede

J.L.P. Benesch

J.E. Deane

C.M. Tang

C.V. Robinson

S.M. Lea



Abstract

Flagellar type III secretion systems (T3SS) contain an essential cytoplasmic-ring (C-ring) largely composed of two proteins FliM and FliN, whereas an analogous substructure for the closely related non-flagellar (NF) T3SS has not been observed in situ. We show that the spa33 gene encoding the putative NF-T3SS C-ring component in Shigella flexneri is alternatively translated to produce both full-length (Spa33-FL) and a short variant (Spa33-C), with both required for secretion. They associate in a 1:2 complex (Spa33-FL/C2) that further oligomerises into elongated arrays in vitro. The structure of Spa33-C2 and identification of an unexpected intramolecular pseudodimer in Spa33-FL reveal a molecular model for their higher order assembly within NF-T3SS. Spa33-FL and Spa33-C are identified as functional counterparts of a FliM–FliN fusion and free FliN respectively. Furthermore, we show that Thermotoga maritima FliM and FliN form a 1:3 complex structurally equivalent to Spa33-FL/C2, allowing us to propose a unified model for C-ring assembly by NF-T3SS and flagellar-T3SS.

Citation

Mcdowell, M., Marcoux, J., Mcvicker, G., Johnson, S., Fong, Y., Stevens, R., …Lea, S. (2016). Characterisation of Shigella Spa33 and Thermotoga FliM/N reveals a new model for C-ring assembly in T3SS. Molecular Microbiology, 99(4), 749-766. https://doi.org/10.1111/mmi.13267

Journal Article Type Article
Acceptance Date Nov 2, 2015
Online Publication Date Dec 23, 2015
Publication Date Feb 12, 2016
Deposit Date Jul 26, 2017
Publicly Available Date Aug 7, 2017
Journal Molecular Microbiology
Print ISSN 0950-382X
Electronic ISSN 1365-2958
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 99
Issue 4
Pages 749-766
DOI https://doi.org/10.1111/mmi.13267

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Publisher Licence URL
http://creativecommons.org/licenses/by/4.0/

Copyright Statement
© 2015 The Authors. Molecular Microbiology published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.





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