Dataset Information

Common and distinct structural features of Salmonella injectisome and flagellar basal body.

ABSTRACT: Bacterial pathogens use an injectisome to deliver virulence proteins into eukaryotic host cells. The bacterial flagellum and injectisome export their component proteins for self-assembly. These two systems show high structural similarities and are classified as the type III secretion system, but it remains elusive how similar they are in situ because the structures of these complexes isolated from cells and visualized by electron cryomicroscopy have shown only the export channel and housing for the export apparatus. Here we report in situ structures of Salmonella injectisome and flagellum by electron cryotomography. The injectisome lacks the flagellar basal body C-ring, but a wing-like disc and a globular density corresponding to the export gate platform and ATPase hexamer ring, respectively, are stably attached through thin connectors, revealing yet unidentified common architectures of the two systems. The ATPase ring is far from the disc, suggesting that both apparatuses are observed in an export-off state.

SUBMITTER: Kawamoto A

PROVIDER: S-EPMC3842551 | biostudies-literature | 2013 Nov

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Common and distinct structural features of Salmonella injectisome and flagellar basal body.

Kawamoto Akihiro A Morimoto Yusuke V YV Miyata Tomoko T Minamino Tohru T Hughes Kelly T KT Kato Takayuki T Namba Keiichi K

Scientific reports 20131128

Bacterial pathogens use an injectisome to deliver virulence proteins into eukaryotic host cells. The bacterial flagellum and injectisome export their component proteins for self-assembly. These two systems show high structural similarities and are classified as the type III secretion system, but it remains elusive how similar they are in situ because the structures of these complexes isolated from cells and visualized by electron cryomicroscopy have shown only the export channel and housing for ...[more]

PMID: 24284544

Similar Datasets

Project description:The opportunistic pathogen Pseudomonas aeruginosa utilizes an injectisome-type III secretion system (injectisome-T3SS) to elicit cytotoxicity toward epithelial cells and macrophages. Macrophage killing results from the cytotoxic properties of the translocated effector proteins (ExoS, ExoT, ExoU, and ExoY) and inflammasome-mediated induction of pyroptosis. Inflammasome activation can occur following Nlrc4-mediated recognition of cytosolic translocated flagellin (FliC). In the present study, we demonstrate that FliC is a secretion substrate of both the injectisome- and flagellum-associated T3SSs. Molecular analyses indicate that the first 20 amino-terminal residues of FliC are sufficient for secretion by the injectisome-T3SS and that the first 100 residues are sufficient for translocation of FliC into host cells. Although maximal inflammasome activation requires FliC, activation can also occur in the absence of FliC. This prompted us to examine whether other flagellar components might also be translocated into cells to elicit inflammasome activation. Indeed, we find that the flagellar cap (FliD), hook-associated (FlgK and FlgL), hook (FlgE), and rod (FlgE) proteins are secretion substrates of the injectisome-T3SS. None of these proteins, however, result in increased inflammasome activation when they are overexpressed in a fliC mutant and appear to be translocated into host cells. While a role in inflammasome activation has been excluded, these data raise the possibility that flagellar components, which are highly conserved between different bacterial species, trigger other specific host responses from the extracellular milieu or contribute to the pathogenesis of P. aeruginosa.The inflammasome is a host defense mechanism that recognizes invading bacteria and triggers an inflammatory immune response. The opportunistic pathogen P. aeruginosa produces both inflammasome agonists and antagonists. In this study, we demonstrate that overexpression of an agonist suppresses the activity of an antagonist, thereby resulting in inflammasome activation. Since the relative expression levels of agonists and antagonists likely vary between strains, these differences could be important predictors of whether a particular P. aeruginosa strain elicits inflammasome activation.

Project description:UnlabelledFlagellar biogenesis in Helicobacter pylori is regulated by a transcriptional hierarchy governed by three sigma factors, RpoD (σ(80)), RpoN (σ(54)), and FliA (σ(28)), that temporally coordinates gene expression with the assembly of the flagellum. Previous studies showed that loss of flagellar protein export apparatus components inhibits transcription of flagellar genes. The FlgS/FlgR two-component system activates transcription of RpoN-dependent genes though an unknown mechanism. To understand better the extent to which flagellar gene regulation is coupled to flagellar assembly, we disrupted flagellar biogenesis at various points and determined how these mutations affected transcription of RpoN-dependent (flaB and flgE) and FliA-dependent (flaA) genes. The MS ring (encoded by fliF) is one of the earliest flagellar structures assembled. Deletion of fliF resulted in the elimination of RpoN-dependent transcripts and an ∼4-fold decrease in flaA transcript levels. FliH is a cytoplasmic protein that functions with the C ring protein FliN to shuttle substrates to the export apparatus. Deletions of fliH and genes encoding C ring components (fliM and fliY) decreased transcript levels of flaB and flgE but had little or no effect on transcript levels of flaA. Transcript levels of flaB and flgE were elevated in mutants where genes encoding rod proteins (fliE and flgBC) were deleted, while transcript levels of flaA was reduced ∼2-fold in both mutants. We propose that FlgS responds to an assembly checkpoint associated with the export apparatus and that FliH and one or more C ring component assist FlgS in engaging this flagellar structure.ImportanceThe mechanisms used by bacteria to couple transcription of flagellar genes with assembly of the flagellum are poorly understood. The results from this study identified components of the H. pylori flagellar basal body that either positively or negatively affect expression of RpoN-dependent flagellar genes. Some of these basal body proteins may interact directly with regulatory proteins that control transcription of the H. pylori RpoN regulon, a hypothesis that can be tested by examining protein-protein interactions in vitro.

Dataset Information

Common and distinct structural features of Salmonella injectisome and flagellar basal body.

Publications

Common and distinct structural features of Salmonella injectisome and flagellar basal body.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets