Characterisation ofShigella Spa33 andThermotoga FliM/N reveals a new model for C-ring assembly in T3SS

McDowell, MA, Marcoux, J, McVicker, G ORCID: 0000-0002-6967-5968, Johnson, S, Fong, YH, Stevens, R, Bowman, LAH, Degiacomi, MT, Yan, J, Wise, A, Friede, ME, Benesch, JLP, Deane, JE, Tang, CM, Robinson, CV and Lea, SM, 2016. Characterisation ofShigella Spa33 andThermotoga FliM/N reveals a new model for C-ring assembly in T3SS. Molecular Microbiology, 99 (4), pp. 749-766. ISSN 0950-382X

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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.

Item Type: Journal article
Publication Title: Molecular Microbiology
Creators: 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. and Lea, S.M.
Publisher: Wiley-Blackwell
Date: February 2016
Volume: 99
Number: 4
ISSN: 0950-382X
Divisions: Schools > School of Science and Technology
Depositing User: Jonathan Gallacher
Date Added: 12 Jan 2017 12:09
Last Modified: 09 Jun 2017 14:10

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