Flagellar filament elongation can be impaired by mutations in the hook protein FlgE of <i>Salmonella typhimurium</i>: a possible role of the hook as a passage for the anti‐sigma factor FlgM

Saitō, Tsunemasa; Ueno, Takamasa; Kubori, Tomoko; Yamaguchi, Shigeru; Iino, Tetsuo; Aizawa, Shin‐Ichi

doi:10.1046/j.1365-2958.1998.00738.x

Cited by 14 publications

(12 citation statements)

References 36 publications

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“…In this strain, the export of FlgM was depen- dent on the NaCl concentration. Observation of the swimming behavior of this strain at a concentration of NaCl allowing good flagellation suggested that the function of the hook had deteriorated, since the flagellar bundles were not as tight as those of the wild-type cells (25). In the case of R. sphaeroides, a strain showing a curved hook produced normal amounts of flagellin, but the swimming behavior both in swarm plates as well as in liquid medium was altered.…”

Section: Discussionmentioning

confidence: 93%

“…The amplification product was cloned into the unique EcoRI site of pRS4303 located after amino acid 40 from the predicted FlgE sequence. The 5.5-kb PstI fragment carrying flgE::aad was subcloned into pJQ200mp18 (25). The resulting plasmid was introduced by transformation into E. coli S17-1 and subsequently transferred to R. sphaeroides by conjugation.…”

Section: Methodsmentioning

confidence: 99%

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The Hook Gene ( flgE ) Is Expressed from the flgBCDEF Operon in Rhodobacter sphaeroides : Study of an flgE Mutant

Ballado

Camarena²,

González‐Pedrajo

et al. 2001

J Bacteriol

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In this work we identified the flgE gene encoding the flagellar hook protein from Rhodobacter sphaeroides. Our results show that this gene is part of a flagellar cluster that includes the genes flgB, flgC, flgD, flgE, and flgF. Two different types of mutants in the flgE gene were isolated, and both showed a Fla ؊ phenotype, indicating the functionality of this sequence. Complementation studies of these mutant strains suggest that flgE is included in a single transcriptional unit that starts in flgB and ends in flgF. In agreement with this possibility, a specific transcript of approximately 3.5 kb was identified by Northern blot. This mRNA is large enough to represent the complete flgBCDEF operon. FlgE showed a relatively high proline content; in particular, a region of 12 amino acids near the N terminus, in which four prolines were identified. Cells expressing a mutant FlgE protein lacking this region showed abnormal swimming behavior, and their hooks were curved. These results suggest that this region is involved in the characteristic quaternary structure of the hook of R. sphaeroides and also imply that a straight hook, or perhaps the rigidity associated with this feature, is important for an efficient swimming behavior in this bacterium.Salmonella enterica serovar Typhimurium swims toward favorable environments in response to changes in the surrounding medium using its flagella; these appendages consist basically of a helical filament driven by a rotary motor. When flagella rotate in counterclockwise direction, the filaments coalesce in a bundle that functions as a propeller to push the bacterial cell body in a linear trajectory. On the contrary, when flagella reverse the sense of rotation the bundle is no longer stable, and the uncoordinated movement of each flagellum causes the cell to tumble. As revealed by early studies of electron microscopy, the flagellum consists of a filament, a curved hook, and a basal body (6). The filament and the hook are each composed of repeats of a single protein, flagellin and hook protein, respectively. These polypeptides do not share extensive similarity at the level of its primary sequence but both have the ability to self-assemble, and the resulting structures are capable of displaying polymorphic transitions; this capability has been suggested to be important in the motility of certain species of bacteria (12,16,22).The structure of the filament has been the subject of extensive study during the last few decades, and various structural models have been proposed (18,21,33,37). In contrast, the hook structure has been less well characterized; however, since the hook protein shares important features with flagellin, it has been suggested that hook and flagellin subunits have a similar folding pattern (20,34,35,36).The detailed knowledge about the structure and function of the flagellum in enterobacteria contrasts strongly with the limited data on these aspects that exist for other bacterial groups. However, it seems clear that as far as structure and function are concerned, ...

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Section: Discussionmentioning

confidence: 93%

Section: Methodsmentioning

confidence: 99%

The Hook Gene ( flgE ) Is Expressed from the flgBCDEF Operon in Rhodobacter sphaeroides : Study of an flgE Mutant

Ballado

Camarena²,

González‐Pedrajo

et al. 2001

J Bacteriol

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“…Following completion of the hook-basal body, secretion of the FlgM anti- 28 factor occurs by this pathway (52,108). The work presented below is a characterization of the determinants contained within FlgM that are required for it to be specifically recognized and secreted by this pathway (20).…”

Section: Flgm Secreted By a Flagellar Type III Pathwaymentioning

confidence: 99%

“…The transcriptional hierarchy of the flagellum pathway is one mechanism that leads to the efficient assembly of the flagellum following induction of the pathway. FlgM is secreted following the completion of the hook-basal body intermediate structure (52,108). This results in the full induction of class 3 promoter transcription.…”

Section: Link Between Regulation Of Expression and Efficiency Of Assementioning

confidence: 99%

Coupling of Flagellar Gene Expression to Flagellar Assembly in Salmonella enterica Serovar Typhimurium and Escherichia coli

Chilcott

Hughes

2000

Microbiol Mol Biol Rev

593

554

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SUMMARY How do organisms assess the degree of completion of a large structure, especially an extracellular structure such as a flagellum? Bacteria can do this. Mutants that lack key components needed early in assembly fail to express proteins that would normally be added at later assembly stages. In some cases, the regulatory circuitry is able to sense completion of structures beyond the cell surface, such as completion of the external hook structure. In Salmonella and Escherichia coli, regulation occurs at both transcriptional and posttranscriptional levels. One transcriptional regulatory mechanism involves a regulatory protein, FlgM, that escapes from the cell (and thus can no longer act) through a complete flagellum and is held inside when the structure has not reached a later stage of completion. FlgM prevents late flagellar gene transcription by binding the flagellum-specific transcription factor ς28. FlgM is itself regulated in response to the assembly of an incomplete flagellum known as the hook-basal body intermediate structure. Upon completion of the hook-basal body structure, FlgM is exported through this structure out of the cell. Inhibition of ς28-dependent transcription is relieved, and genes required for the later assembly stages are expressed, allowing completion of the flagellar organelle. Distinct posttranscriptional regulatory mechanisms occur in response to assembly of the flagellar type III secretion apparatus and of ring structures in the peptidoglycan and lipopolysaccharide layers. The entire flagellar regulatory pathway is regulated in response to environmental cues. Cell cycle control and flagellar development are codependent. We discuss how all these levels of regulation ensure efficient assembly of the flagellum in response to environmental stimuli.

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“…In P. aeruginosa , the flagellar hook is formed by polymerization of approximately 120 single molecules named flagellar hook protein E (FlgE) (NP_249771), encoded by the flagellar hook protein gene, flgE (GeneID: 878285). In addition to providing flexibility and power conversion between the basal body and the filament, FlgE is also involved in the elongation or assembly of the filament, and flgE mutations often result in structural abnormality or deficiency in multiple bacterial species 10–13 . However, additional roles that this protein may play, as either an isolated monomer or a polymer in the hook, remain unclear except for a few reports on the antigenicity of FlgE in bacterial infections 14–16 .…”

Section: Introductionmentioning

confidence: 99%

Flagellar Hooks and Hook Protein FlgE Participate in Host Microbe Interactions at Immunological Level

Shen

Chen

Wang

et al. 2017

Sci Rep

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Host-microbe interactions determine the outcome of host responses to commensal and pathogenic microbes. Previously, two epithelial cell-binding peptides were found to be homologues of two sites (B, aa168–174; F, aa303–309) in the flagellar hook protein FlgE of Pseudomonas aeruginosa. Tertiary modeling predicted these sites at the interface of neighboring FlgE monomers in the fully formed hook. Recombinant FlgE protein stimulated proinflammatory cytokine production in a human cell line and in murine lung organoid culture as detected with real-time RT-PCR and ELISA assays. When administered to mice, FlgE induced lung inflammation and enhanced the Th2-biased humoral response to ovalbumin. A pull-down assay performed with FlgE-saturated resin identified caveolin-1 as an FlgE-binding protein, and caveolin-1 deficiency impaired FlgE-induced inflammation and downstream Erk1/2 pathway activation in lung organoids. Intact flagellar hooks from bacteria were also proinflammatory. Mutations to sites B and F impaired bacteria motility and proinflammatory potency of FlgE without altering adjuvanticity of FlgE. These findings suggest that the flagellar hook and FlgE are novel players in host-bacterial interactions at immunological level. Further studies along this direction would provide new opportunities for understanding and management of diseases related with bacterial infection.

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Flagellar filament elongation can be impaired by mutations in the hook protein FlgE of Salmonella typhimurium: a possible role of the hook as a passage for the anti‐sigma factor FlgM

Cited by 14 publications

References 36 publications

The Hook Gene ( flgE ) Is Expressed from the flgBCDEF Operon in Rhodobacter sphaeroides : Study of an flgE Mutant

The Hook Gene ( flgE ) Is Expressed from the flgBCDEF Operon in Rhodobacter sphaeroides : Study of an flgE Mutant

Coupling of Flagellar Gene Expression to Flagellar Assembly in Salmonella enterica Serovar Typhimurium and Escherichia coli

Flagellar Hooks and Hook Protein FlgE Participate in Host Microbe Interactions at Immunological Level

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