In:
Molecular Microbiology, Wiley, Vol. 99, No. 4 ( 2016-02), p. 749-766
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 S higella flexneri is alternatively translated to produce both full‐length ( S pa33‐ FL ) and a short variant ( S pa33‐ C ), with both required for secretion. They associate in a 1:2 complex ( S pa33‐ FL /C 2 ) that further oligomerises into elongated arrays in vitro . The structure of S pa33‐ C 2 and identification of an unexpected intramolecular pseudodimer in S pa33‐ FL reveal a molecular model for their higher order assembly within NF ‐ T3SS . S pa33‐ FL and S pa33‐ C are identified as functional counterparts of a FliM – FliN fusion and free FliN respectively. Furthermore, we show that T hermotoga maritima FliM and FliN form a 1:3 complex structurally equivalent to S pa33‐ FL /C 2 , allowing us to propose a unified model for C ‐ring assembly by NF ‐ T3SS and flagellar‐ T3SS .
Type of Medium:
Online Resource
ISSN:
0950-382X
,
1365-2958
DOI:
10.1111/mmi.2016.99.issue-4
Language:
English
Publisher:
Wiley
Publication Date:
2016
detail.hit.zdb_id:
1501537-3
