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Halte M, Andrianova EP, Goosmann C, Chevance FFV, Hughes KT, Zhulin IB, Erhardt M. FlhE functions as a chaperone to prevent formation of periplasmic flagella in Gram-negative bacteria. Nat Commun 2024; 15:5921. [PMID: 39004688 PMCID: PMC11247099 DOI: 10.1038/s41467-024-50278-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Accepted: 07/04/2024] [Indexed: 07/16/2024] Open
Abstract
The bacterial flagellum, which facilitates motility, is composed of ~20 structural proteins organized into a long extracellular filament connected to a cytoplasmic rotor-stator complex via a periplasmic rod. Flagellum assembly is regulated by multiple checkpoints that ensure an ordered gene expression pattern coupled to the assembly of the various building blocks. Here, we use epifluorescence, super-resolution, and transmission electron microscopy to show that the absence of a periplasmic protein (FlhE) prevents proper flagellar morphogenesis and results in the formation of periplasmic flagella in Salmonella enterica. The periplasmic flagella disrupt cell wall synthesis, leading to a loss of normal cell morphology resulting in cell lysis. We propose that FlhE functions as a periplasmic chaperone to control assembly of the periplasmic rod, thus preventing formation of periplasmic flagella.
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Affiliation(s)
- Manuel Halte
- Institute of Biology, Humboldt-Universität zu Berlin, Philippstr. 13, 10115, Berlin, Germany.
| | | | - Christian Goosmann
- Max Planck Institute for Infection Biology, Charitéplatz 1, 10117, Berlin, Germany
| | | | - Kelly T Hughes
- School of Biological Sciences, University of Utah, Salt Lake City, UT, USA
| | - Igor B Zhulin
- Department of Microbiology, The Ohio State University, Columbus, OH, 43210, USA
| | - Marc Erhardt
- Institute of Biology, Humboldt-Universität zu Berlin, Philippstr. 13, 10115, Berlin, Germany.
- Max Planck Unit for the Science of Pathogens, Charitéplatz 1, 10117, Berlin, Germany.
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2
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Kinoshita M, Minamino T, Uchihashi T, Namba K. FliH and FliI help FlhA bring strict order to flagellar protein export in Salmonella. Commun Biol 2024; 7:366. [PMID: 38531947 DOI: 10.1038/s42003-024-06081-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Accepted: 03/20/2024] [Indexed: 03/28/2024] Open
Abstract
The flagellar type III secretion system (fT3SS) switches substrate specificity from rod-hook-type to filament-type upon hook completion, terminating hook assembly and initiating filament assembly. The C-terminal cytoplasmic domain of FlhA (FlhAC) forms a homo-nonameric ring and is directly involved in substrate recognition, allowing the fT3SS to coordinate flagellar protein export with assembly. The highly conserved GYXLI motif (residues 368-372) of FlhAC induces dynamic domain motions of FlhAC required for efficient and robust flagellar protein export by the fT3SS, but it remains unknown whether this motif is also important for ordered protein export by the fT3SS. Here we analyzed two GYXLI mutants, flhA(GAAAA) and flhA(GGGGG), and provide evidence suggesting that the GYXLI motif in FlhAC requires the flagellar ATPase complex not only to efficiently remodel the FlhAC ring structure for the substrate specificity switching but also to correct substrate recognition errors that occur during flagellar assembly.
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Affiliation(s)
- Miki Kinoshita
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan.
| | - Takayuki Uchihashi
- Department of Physics, Nagoya University, Chikusa-ku, Nagoya, 464-8602, Japan
| | - Keiichi Namba
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
- JEOL YOKOGUSHI Research Alliance Laboratories, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
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3
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Bryant OJ, Fraser GM. Identification of a new export signal that targets early subunits to the flagellar type III secretion export machinery. mBio 2024; 15:e0306723. [PMID: 38376149 PMCID: PMC10936197 DOI: 10.1128/mbio.03067-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Accepted: 01/26/2024] [Indexed: 02/21/2024] Open
Abstract
Type III secretion systems (T3SSs) are essential for motility and virulence in many bacterial pathogens. Proteins destined for the flagellar T3SS contain at least two export signals in their N-terminal D0 domain. Here, we describe a third carboxy (C)-terminal signal in early flagellar subunits that facilitates subunit targeting to the export machinery. Mutational analysis identified critical residues within the flagellar hook subunit C-terminal export signal. The flagellar ATPase and cytoplasmic ring components were not required for this targeting, indicating that core export machinery components facilitate substrate targeting via the C-terminal export signal. More broadly, these results demonstrate that multiple distinct export signals within type III secretion substrates facilitate distinct export events at the T3SS export machinery. Our data establish key events in the export mechanism of type III secretion systems: targeting of subunits to and their sequential interactions with key components of the export machinery. IMPORTANCE Many bacterial pathogens utilize T3SS to inject virulence proteins (effectors) into host cells or to assemble flagella on the bacterial cell surface. Bacterial flagella present a paradigm for how cells build and operate complex cell-surface "nanomachines." Efficient subunit targeting from the bacterial cytosol to type III secretion systems is essential for rapid assembly and secretion by T3SSs. Subunits are thought to dock at the export machinery before being unfolded and translocated into the export channel. However, little is known about how subunits dock at the export machinery and the events that occur post docking. Here, we identified a new export signal within the C-termini of subunits that is essential for targeting of subunits to the type III export machinery. We show that this new export signal and previously identified export signals are recognized separately and sequentially, revealing a pathway for subunit transit through the type III export machinery in which sequential recognition events carry out different roles at major steps in the export pathway.
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Affiliation(s)
- Owain J. Bryant
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge, United Kingdom
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Gillian M. Fraser
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge, United Kingdom
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4
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Dhindwal P, Boniecki MT, Moore SA. Helicobacter pylori FlgN binds its substrate FlgK and the flagellum ATPase FliI in a similar manner observed for the FliT chaperone. Protein Sci 2024; 33:e4882. [PMID: 38151822 PMCID: PMC10804663 DOI: 10.1002/pro.4882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 12/19/2023] [Accepted: 12/20/2023] [Indexed: 12/29/2023]
Abstract
In bacterial flagellum biogenesis, secretion of the hook-filament junction proteins FlgK and FlgL and completion of the flagellum requires the FlgN chaperone. Similarly, the related FliT chaperone is necessary for the secretion of the filament cap protein FliD and binds the flagellar export gate protein FlhA and the flagellum ATPase FliI. FlgN and FliT require FliJ for effective substrate secretion. In Helicobacter pylori, neither FlgN, FliT, nor FliJ have been annotated. We demonstrate that the genome location of HP1120 is identical to that of flgN in other flagellated bacteria and that HP1120 is the homolog of Campylobacter jejuni FlgN. A modeled HP1120 structure contains three α-helices and resembles the FliT chaperone, sharing a similar substrate-binding pocket. Using pulldowns and thermophoresis, we show that both HP1120 and a HP1120Δ126-144 deletion mutant bind to FlgK with nanomolar affinity, but not to the filament cap protein FliD, confirming that HP1120 is FlgN. Based on size-exclusion chromatography and multi-angle light scattering, H. pylori FlgN binds to FlgK with 1:1 stoichiometry. Overall structural similarities between FlgN and FliT suggest that substrate recognition on FlgN primarily involves an antiparallel coiled-coil interface between the third helix of FlgN and the C-terminal helix of the substrate. A FlgNΔ126-144 N100A, Y103A, S111I triple mutant targeting this interface significantly impairs the binding of FlgK. Finally, we demonstrate that FlgNΔ126-144 , like FliT, binds with sub-micromolar affinity to the flagellum ATPase FliI or its N-terminal domain. Hence FlgN and FliT likely couple delivery of low-abundance export substrates to the flagellum ATPase FliI.
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Affiliation(s)
- Poonam Dhindwal
- Department of Biochemistry, Microbiology and ImmunologyCollege of Medicine, University of SaskatchewanSaskatoonCanada
| | - Michal T. Boniecki
- Department of Biochemistry, Microbiology and ImmunologyCollege of Medicine, University of SaskatchewanSaskatoonCanada
| | - Stanley A. Moore
- Department of Biochemistry, Microbiology and ImmunologyCollege of Medicine, University of SaskatchewanSaskatoonCanada
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5
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Wimmi S, Fleck M, Helbig C, Brianceau C, Langenfeld K, Szymanski WG, Angelidou G, Glatter T, Diepold A. Pilotins are mobile T3SS components involved in assembly and substrate specificity of the bacterial type III secretion system. Mol Microbiol 2024; 121:304-323. [PMID: 38178634 DOI: 10.1111/mmi.15223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 12/17/2023] [Accepted: 12/20/2023] [Indexed: 01/06/2024]
Abstract
In animal pathogens, assembly of the type III secretion system injectisome requires the presence of so-called pilotins, small lipoproteins that assist the formation of the secretin ring in the outer membrane. Using a combination of functional assays, interaction studies, proteomics, and live-cell microscopy, we determined the contribution of the pilotin to the assembly, function, and substrate selectivity of the T3SS and identified potential new downstream roles of pilotin proteins. In absence of its pilotin SctG, Yersinia enterocolitica forms few, largely polar injectisome sorting platforms and needles. Accordingly, most export apparatus subcomplexes are mobile in these strains, suggesting the absence of fully assembled injectisomes. Remarkably, while absence of the pilotin all but prevents export of early T3SS substrates, such as the needle subunits, it has little effect on secretion of late T3SS substrates, including the virulence effectors. We found that although pilotins interact with other injectisome components such as the secretin in the outer membrane, they mostly localize in transient mobile clusters in the bacterial membrane. Together, these findings provide a new view on the role of pilotins in the assembly and function of type III secretion injectisomes.
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Affiliation(s)
- Stephan Wimmi
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Moritz Fleck
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Carlos Helbig
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Corentin Brianceau
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Katja Langenfeld
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Witold G Szymanski
- Mass Spectrometry and Proteomics Facility, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Georgia Angelidou
- Mass Spectrometry and Proteomics Facility, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Timo Glatter
- Mass Spectrometry and Proteomics Facility, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Andreas Diepold
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
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6
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Minamino T, Kinoshita M. Structure, Assembly, and Function of Flagella Responsible for Bacterial Locomotion. EcoSal Plus 2023; 11:eesp00112023. [PMID: 37260402 PMCID: PMC10729930 DOI: 10.1128/ecosalplus.esp-0011-2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Accepted: 04/14/2023] [Indexed: 01/28/2024]
Abstract
Many motile bacteria use flagella for locomotion under a variety of environmental conditions. Because bacterial flagella are under the control of sensory signal transduction pathways, each cell is able to autonomously control its flagellum-driven locomotion and move to an environment favorable for survival. The flagellum of Salmonella enterica serovar Typhimurium is a supramolecular assembly consisting of at least three distinct functional parts: a basal body that acts as a bidirectional rotary motor together with multiple force generators, each of which serves as a transmembrane proton channel to couple the proton flow through the channel with torque generation; a filament that functions as a helical propeller that produces propulsion; and a hook that works as a universal joint that transmits the torque produced by the rotary motor to the helical propeller. At the base of the flagellum is a type III secretion system that transports flagellar structural subunits from the cytoplasm to the distal end of the growing flagellar structure, where assembly takes place. In recent years, high-resolution cryo-electron microscopy (cryoEM) image analysis has revealed the overall structure of the flagellum, and this structural information has made it possible to discuss flagellar assembly and function at the atomic level. In this article, we describe what is known about the structure, assembly, and function of Salmonella flagella.
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Affiliation(s)
- Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
| | - Miki Kinoshita
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
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7
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Fanelli F, Montemurro M, Chieffi D, Cho GS, Low HZ, Hille F, Franz CMAP, Fusco V. Motility in Periweissella Species: Genomic and Phenotypic Characterization and Update on Motility in Lactobacillaceae. Microorganisms 2023; 11:2923. [PMID: 38138067 PMCID: PMC10745875 DOI: 10.3390/microorganisms11122923] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 11/24/2023] [Accepted: 11/28/2023] [Indexed: 12/24/2023] Open
Abstract
The genus Weissella and the recently described genus Periweissella, to which some previously named Weissella species have been reclassified as a result of a taxogenomic assessment, includes lactic acid bacteria species with high biotechnological and probiotic potential. Only one species, namely, Periweissella (P.) beninensis, whose type strain has been shown to possess probiotic features, has so far been described to be motile. However, the availability of numerous genome sequences of Weissella and Periweissella species prompted the possibility to screen for the presence of the genetic determinants encoding motility in Weissella and Periweissellas spp. other than P. beninensis. Herein, we performed a comprehensive genomic analysis to identify motility-related proteins in all Weissella and Periweissella species described so far, and extended the analysis to the recently sequenced Lactobacillaceae spp. Furthermore, we performed motility assays and transmission electron microscopy (TEM) on Periweissella type strains to confirm the genomic prediction. The homology-based analysis revealed genes coding for motility proteins only in the type strains of P. beninensis, P. fabalis, P. fabaria and P. ghanensis genomes. However, only the P. beninensis type strain was positive in the motility assay and displayed run-and-tumble behavior. Many peritrichous and long flagella on bacterial cells were visualized via TEM, as well. As for the Lactobacillaceae, in addition to the species previously described to harbor motility proteins, the genetic determinants of motility were also found in the genomes of the type strains of Lactobacillus rogosae and Ligilactobacillus salitolerans. This study, which is one of the first to analyze the genomes of Weissella, Periweissella and the recently sequenced Lactobacillaceae spp. for the presence of genes coding for motility proteins and which assesses the associated motility phenotypes, provides novel results that expand knowledge on these genera and are useful in the further characterization of lactic acid bacteria.
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Affiliation(s)
- Francesca Fanelli
- National Research Council of Italy, Institute of Sciences of Food Production (CNR-ISPA), 70126 Bari, Italy; (F.F.); (M.M.); (D.C.)
| | - Marco Montemurro
- National Research Council of Italy, Institute of Sciences of Food Production (CNR-ISPA), 70126 Bari, Italy; (F.F.); (M.M.); (D.C.)
| | - Daniele Chieffi
- National Research Council of Italy, Institute of Sciences of Food Production (CNR-ISPA), 70126 Bari, Italy; (F.F.); (M.M.); (D.C.)
| | - Gyu-Sung Cho
- Department of Microbiology and Biotechnology, Max Rubner-Institut, 24103 Kiel, Germany; (G.-S.C.); (H.-Z.L.); (F.H.)
| | - Hui-Zhi Low
- Department of Microbiology and Biotechnology, Max Rubner-Institut, 24103 Kiel, Germany; (G.-S.C.); (H.-Z.L.); (F.H.)
| | - Frank Hille
- Department of Microbiology and Biotechnology, Max Rubner-Institut, 24103 Kiel, Germany; (G.-S.C.); (H.-Z.L.); (F.H.)
| | - Charles M. A. P. Franz
- Department of Microbiology and Biotechnology, Max Rubner-Institut, 24103 Kiel, Germany; (G.-S.C.); (H.-Z.L.); (F.H.)
| | - Vincenzina Fusco
- National Research Council of Italy, Institute of Sciences of Food Production (CNR-ISPA), 70126 Bari, Italy; (F.F.); (M.M.); (D.C.)
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8
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Rossi P, Xing Q, Bini E, Portaliou AG, Clay MC, Warren EM, Khanra NK, Economou A, Kalodimos CG. Chaperone Recycling in Late-Stage Flagellar Assembly. J Mol Biol 2023; 435:167954. [PMID: 37330284 PMCID: PMC10471782 DOI: 10.1016/j.jmb.2023.167954] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 12/30/2022] [Accepted: 01/03/2023] [Indexed: 06/19/2023]
Abstract
The flagellum is a sophisticated nanomachine responsible for motility in Gram-negative bacteria. Flagellar assembly is a strictly choreographed process, in which the motor and export gate are formed first, followed by the extracellular propeller structure. Extracellular flagellar components are escorted to the export gate by dedicated molecular chaperones for secretion and self-assembly at the apex of the emerging structure. The detailed mechanisms of chaperone-substrate trafficking at the export gate remain poorly understood. Here, we structurally characterized the interaction of Salmonella enterica late-stage flagellar chaperones FliT and FlgN with the export controller protein FliJ. Previous studies showed that FliJ is absolutely required for flagellar assembly since its interaction with chaperone-client complexes controls substrate delivery to the export gate. Our biophysical and cell-based data show that FliT and FlgN bind FliJ cooperatively, with high affinity and on specific sites. Chaperone binding completely disrupts the FliJ coiled-coil structure and alters its interactions with the export gate. We propose that FliJ aids the release of substrates from the chaperone and forms the basis of chaperone recycling during late-stage flagellar assembly.
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Affiliation(s)
- Paolo Rossi
- Deparment of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, United States
| | - Qiong Xing
- State Key Laboratory of Bio-catalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan 430074, China
| | - Elisabetta Bini
- Deparment of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, United States
| | - Athina G Portaliou
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
| | - Mary C Clay
- Deparment of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, United States
| | - Eric M Warren
- Deparment of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, United States
| | - Nandish K Khanra
- Deparment of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, United States
| | - Anastassios Economou
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
| | - Charalampos G Kalodimos
- Deparment of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, United States.
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9
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Minamino T, Kinoshita M, Morimoto YV, Namba K. Activation mechanism of the bacterial flagellar dual-fuel protein export engine. Biophys Physicobiol 2022; 19:e190046. [PMID: 36567733 PMCID: PMC9751260 DOI: 10.2142/biophysico.bppb-v19.0046] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Accepted: 11/17/2022] [Indexed: 11/19/2022] Open
Abstract
Bacteria employ the flagellar type III secretion system (fT3SS) to construct flagellum, which acts as a supramolecular motility machine. The fT3SS of Salmonella enterica serovar Typhimurium is composed of a transmembrane export gate complex and a cytoplasmic ATPase ring complex. The transmembrane export gate complex is fueled by proton motive force across the cytoplasmic membrane and is divided into four distinct functional parts: a dual-fuel export engine; a polypeptide channel; a membrane voltage sensor; and a docking platform. ATP hydrolysis by the cytoplasmic ATPase complex converts the export gate complex into a highly efficient proton (H+)/protein antiporter that couples inward-directed H+ flow with outward-directed protein export. When the ATPase ring complex does not work well in a given environment, the export gate complex will remain inactive. However, when the electric potential difference, which is defined as membrane voltage, rises above a certain threshold value, the export gate complex becomes an active H+/protein antiporter to a considerable degree, suggesting that the export gate complex has a voltage-gated activation mechanism. Furthermore, the export gate complex also has a sodium ion (Na+) channel to couple Na+ influx with flagellar protein export. In this article, we review our current understanding of the activation mechanism of the dual-fuel protein export engine of the fT3SS. This review article is an extended version of a Japanese article, Membrane voltage-dependent activation of the transmembrane export gate complex in the bacterial flagellar type III secretion system, published in SEIBUTSU BUTSURI Vol. 62, p165-169 (2022).
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Affiliation(s)
- Tohru Minamino
- Graduate school of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
| | - Miki Kinoshita
- Graduate school of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
| | - Yusuke V. Morimoto
- Department of Physics and Information Technology, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, Iizuka, Fukuoka 820-8502, Japan,Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan
| | - Keiichi Namba
- Graduate school of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan,RIKEN SPring-8 Center, Suita, Osaka 565-0871, Japan,JEOL YOKOGUSHI Research Alliance Laboratories, Osaka University, Suita, Osaka 565-0871, Japan
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10
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Conserved GYXLI Motif of FlhA Is Involved in Dynamic Domain Motions of FlhA Required for Flagellar Protein Export. Microbiol Spectr 2022; 10:e0111022. [PMID: 35876582 PMCID: PMC9431611 DOI: 10.1128/spectrum.01110-22] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Flagellar structural subunits are transported via the flagellar type III secretion system (fT3SS) and assemble at the distal end of the growing flagellar structure. The C-terminal cytoplasmic domain of FlhA (FlhAC) serves as a docking platform for export substrates and flagellar chaperones and plays an important role in hierarchical protein targeting and export. FlhAC consists of domains D1, D2, D3, and D4 and adopts open and closed conformations. Gly-368 of Salmonella FlhA is located within the highly conserved GYXLI motif and is critical for the dynamic domain motions of FlhAC. However, it remains unclear how it works. Here, we report that periodic conformational changes of the GYXLI motif induce a remodeling of hydrophobic side chain interaction networks in FlhAC and promote the cyclic open-close domain motions of FlhAC. The temperature-sensitive flhA(G368C) mutation stabilized a completely closed conformation at 42°C through strong hydrophobic interactions between Gln-498 of domain D1 and Pro-667 of domain D4 and between Phe-459 of domain D2 and Pro-646 of domain D4, thereby inhibiting flagellar protein export by the fT3SS. Its intragenic suppressor mutations reorganized the hydrophobic interaction networks in the closed FlhAC structure, restoring the protein export activity of the fT3SS to a significant degree. Furthermore, the conformational flexibility of the GYXLI motif was critical for flagellar protein export. We propose that the conserved GYXLI motif acts as a structural switch to induce the dynamic domain motions of FlhAC required for efficient and rapid protein export by the fT3SS. IMPORTANCE Many motile bacteria employ the flagellar type III secretion system (fT3SS) to construct flagella beyond the cytoplasmic membrane. The C-terminal cytoplasmic domain of FlhA (FlhAC), a transmembrane subunit of the fT3SS, provides binding sites for export substrates and flagellar export chaperones to coordinate flagellar protein export with assembly. FlhAC undergoes cyclic open-close domain motions. The highly conserved Gly-368 residue of FlhA is postulated to be critical for dynamic domain motions of FlhAC. However, it remains unknown how it works. Here, we carried out mutational analysis of FlhAC combined with molecular dynamics simulation and provide evidence that the conformational flexibility of FlhAC by Gly-368 is important for remodeling hydrophobic side chain interaction networks in FlhAC to facilitate its cyclic open-close domain motions, allowing the fT3SS to transport flagellar structural subunits for efficient and rapid flagellar assembly.
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11
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Qu D, Jiang M, Duffin C, Hughes KT, Chevance FFV. Targeting early proximal-rod component substrate FlgB to FlhB for flagellar-type III secretion in Salmonella. PLoS Genet 2022; 18:e1010313. [PMID: 35819991 PMCID: PMC9307174 DOI: 10.1371/journal.pgen.1010313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 07/22/2022] [Accepted: 06/24/2022] [Indexed: 11/18/2022] Open
Abstract
The Salmonella flagellar secretion apparatus is a member of the type III secretion (T3S) family of export systems in bacteria. After completion of the flagellar motor structure, the hook-basal body (HBB), the flagellar T3S system undergoes a switch from early to late substrate secretion, which results in the expression and assembly of the external, filament propeller-like structure. In order to characterize early substrate secretion-signals in the flagellar T3S system, the FlgB, and FlgC components of the flagellar rod, which acts as the drive-shaft within the HBB, were subject to deletion mutagenesis to identify regions of these proteins that were important for secretion. The β-lactamase protein lacking its Sec-dependent secretion signal (Bla) was fused to the C-terminus of FlgB and FlgC and used as a reporter to select for and quantify the secretion of FlgB and FlgC into the periplasm. Secretion of Bla into the periplasm confers resistance to ampicillin. In-frame deletions of amino acids 9 through 18 and amino acids 39 through 58 of FlgB decreased FlgB secretion levels while deleting amino acid 6 through 14 diminished FlgC secretion levels. Further PCR-directed mutagenesis indicated that amino acid F45 of FlgB was critical for secretion. Single amino acid mutagenesis revealed that all amino acid substitutions at F45 of FlgB position impaired rod assembly, which was due to a defect of FlgB secretion. An equivalent F49 position in FlgC was essential for assembly but not for secretion. This study also revealed that a hydrophobic patch in the cleaved C-terminal domain of FlhB is critical for recognition of FlgB at F45. Type III secretion (T3S) is the means by which proteins are secreted from the bacterial cytoplasm to build flagella for motility and injectisome structures that facilitate pathogenesis. T3S is the only secretion system known to date that undergoes a secretion-specificity switch. For the assembly of the bacterial flagellum, the T3S system initially secretes early substrates to build the hook-basal body (HBB), which is the main component that makes up the flagellar motor. Upon HBB completion, the flagellar T3S system becomes specific for late substrates, which make up the long external filament that acts as the propeller of the motility organelle. This work identifies important sites of interaction between an early substrate, FlgB and a target site at the cytoplasmic base of T3S apparatus. A second early substrate, FlgC, lacks the targeting interaction found for FlgB suggesting a mechanism that distinguishes early substrates, and may indicate an order to early substrate secretion to facilitate the order of protein subunit assembly for the flagellum.
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Affiliation(s)
- Daofeng Qu
- Key Laboratory of Food Quality and Safety, School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, China
| | - Mengxue Jiang
- Key Laboratory of Food Quality and Safety, School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, China
| | - Calder Duffin
- School of Biological Sciences, University of Utah, Salt Lake City, Utah, United States of America
| | - Kelly T. Hughes
- School of Biological Sciences, University of Utah, Salt Lake City, Utah, United States of America
| | - Fabienne F. V. Chevance
- School of Biological Sciences, University of Utah, Salt Lake City, Utah, United States of America
- * E-mail:
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12
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Minamino T, Kinoshita M, Namba K. Insight Into Distinct Functional Roles of the Flagellar ATPase Complex for Flagellar Assembly in Salmonella. Front Microbiol 2022; 13:864178. [PMID: 35602071 PMCID: PMC9114704 DOI: 10.3389/fmicb.2022.864178] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 04/13/2022] [Indexed: 11/13/2022] Open
Abstract
Most motile bacteria utilize the flagellar type III secretion system (fT3SS) to construct the flagellum, which is a supramolecular motility machine consisting of basal body rings and an axial structure. Each axial protein is translocated via the fT3SS across the cytoplasmic membrane, diffuses down the central channel of the growing flagellar structure and assembles at the distal end. The fT3SS consists of a transmembrane export complex and a cytoplasmic ATPase ring complex with a stoichiometry of 12 FliH, 6 FliI and 1 FliJ. This complex is structurally similar to the cytoplasmic part of the FOF1 ATP synthase. The export complex requires the FliH12-FliI6-FliJ1 ring complex to serve as an active protein transporter. The FliI6 ring has six catalytic sites and hydrolyzes ATP at an interface between FliI subunits. FliJ binds to the center of the FliI6 ring and acts as the central stalk to activate the export complex. The FliH dimer binds to the N-terminal domain of each of the six FliI subunits and anchors the FliI6-FliJ1 ring to the base of the flagellum. In addition, FliI exists as a hetero-trimer with the FliH dimer in the cytoplasm. The rapid association-dissociation cycle of this hetero-trimer with the docking platform of the export complex promotes sequential transfer of export substrates from the cytoplasm to the export gate for high-speed protein transport. In this article, we review our current understanding of multiple roles played by the flagellar cytoplasmic ATPase complex during efficient flagellar assembly.
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Affiliation(s)
- Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | - Miki Kinoshita
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | - Keiichi Namba
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan.,RIKEN SPring-8 Center and Center for Biosystems Dynamics Research, Osaka, Japan.,JEOL YOKOGUSHI Research Alliance Laboratories, Osaka University, Osaka, Japan
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13
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Niu L, Cai W, Cheng X, Li Z, Ruan J, Li F, Qi K, Tu J. Fur Protein Regulates the Motility of Avian Pathogenic Escherichia coli AE17 Through Promoter Regions of the Flagella Key Genes flhD. Front Vet Sci 2022; 9:854916. [PMID: 35518642 PMCID: PMC9062578 DOI: 10.3389/fvets.2022.854916] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 03/21/2022] [Indexed: 12/01/2022] Open
Abstract
Avian pathogenic Escherichia coli (APEC) is an important pathogen causing several diseases in birds. It is responsible for local and systemic infections in poultry, seriously impeding the development of the poultry industry, and poses a potential risk to public health. The iron absorption regulatory protein Fur and the noncoding RNA, RyhB, that it negatively regulates are important factors in bacterial iron uptake, but the regulation of bacterial virulence genes varies greatly among different bacteria. We found that Fur is very important for the mobility of APEC. The expression of fur and RyhB is extensively regulated in APEC, and RyhB expression is also negatively regulated by Fur. A transcriptomic analysis showed that the genes significantly differentially regulated by Fur are related to cell movement, including pilus- or flagellum-dependent cell motility. To verify these results, we examined the effects of fur knockdown on cell movement by measuring the diameter of the bacteria colonies. Consistent with the RNA sequencing results, the mobility of AE17Δfur was significantly reduced compared with that of the wild type, and it had almost lost its ability to move. Using an electrophoretic mobility assay, we confirmed that the Fur protein directly binds to the promoter region of the key flagellum-related gene flhD, thereby affecting the assembly and synthesis of the APEC flagellum. This study extends our understanding of gene regulation in APEC.
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Affiliation(s)
- Lulu Niu
- Anhui Province Key Laboratory of Veterinary Pathobiology and Disease Control, College of Animal Science and Technology, Anhui Agricultural University, Hefei, China
| | - Weizhen Cai
- Anhui Province Key Laboratory of Veterinary Pathobiology and Disease Control, College of Animal Science and Technology, Anhui Agricultural University, Hefei, China
| | - Xi Cheng
- Anhui Province Key Laboratory of Veterinary Pathobiology and Disease Control, College of Animal Science and Technology, Anhui Agricultural University, Hefei, China
| | - Zhe Li
- Anhui Province Key Laboratory of Veterinary Pathobiology and Disease Control, College of Animal Science and Technology, Anhui Agricultural University, Hefei, China
| | - Jianming Ruan
- Anhui Province Key Laboratory of Veterinary Pathobiology and Disease Control, College of Animal Science and Technology, Anhui Agricultural University, Hefei, China
| | - Fangguo Li
- Anhui Province Key Laboratory of Veterinary Pathobiology and Disease Control, College of Animal Science and Technology, Anhui Agricultural University, Hefei, China
| | - Kezong Qi
- Anhui Province Key Laboratory of Veterinary Pathobiology and Disease Control, College of Animal Science and Technology, Anhui Agricultural University, Hefei, China
| | - Jian Tu
- Anhui Province Key Laboratory of Veterinary Pathobiology and Disease Control, College of Animal Science and Technology, Anhui Agricultural University, Hefei, China
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14
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Bryant OJ, Dhillon P, Hughes C, Fraser GM. Recognition of discrete export signals in early flagellar subunits during bacterial Type III secretion. eLife 2022; 11:66264. [PMID: 35238774 PMCID: PMC8983047 DOI: 10.7554/elife.66264] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 03/02/2022] [Indexed: 11/13/2022] Open
Abstract
Type III Secretion Systems (T3SS) deliver subunits from the bacterial cytosol to nascent cell surface flagella. Early flagellar subunits that form the rod and hook substructures are unchaperoned and contain their own export signals. A gate recognition motif (GRM) docks them at the FlhBc component of the FlhAB-FliPQR export gate, but the gate must then be opened and subunits must be unfolded to pass through the flagellar channel. This induced us to seek further signals on the subunits. Here, we identify a second signal at the extreme N-terminus of flagellar rod and hook subunits and determine that key to the signal is its hydrophobicity. We show that the two export signal elements are recognised separately and sequentially, as the N-terminal signal is recognised by the flagellar export machinery only after subunits have docked at FlhBC via the GRM. The position of the N-terminal hydrophobic signal in the subunit sequence relative to the GRM appeared to be important, as a FlgD deletion variant (FlgDshort), in which the distance between the N-terminal signal and the GRM was shortened, 'stalled' at the export machinery and was not exported. The attenuation of motility caused by FlgDshort was suppressed by mutations that destabilised the closed conformation of the FlhAB-FliPQR export gate, suggesting that the hydrophobic N-terminal signal might trigger opening of the flagellar export gate.
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Affiliation(s)
- Owain J Bryant
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Paraminder Dhillon
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Colin Hughes
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Gillian M Fraser
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
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15
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Minamino T, Morimoto YV, Kinoshita M, Namba K. Multiple Roles of Flagellar Export Chaperones for Efficient and Robust Flagellar Filament Formation in Salmonella. Front Microbiol 2021; 12:756044. [PMID: 34691007 PMCID: PMC8527033 DOI: 10.3389/fmicb.2021.756044] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 09/08/2021] [Indexed: 11/30/2022] Open
Abstract
FlgN, FliS, and FliT are flagellar export chaperones specific for FlgK/FlgL, FliC, and FliD, respectively, which are essential component proteins for filament formation. These chaperones facilitate the docking of their cognate substrates to a transmembrane export gate protein, FlhA, to facilitate their subsequent unfolding and export by the flagellar type III secretion system (fT3SS). Dynamic interactions of the chaperones with FlhA are thought to determine the substrate export order. To clarify the role of flagellar chaperones in filament assembly, we constructed cells lacking FlgN, FliS, and/or FliT. Removal of either FlgN, FliS, or FliT resulted in leakage of a large amount of unassembled FliC monomers into the culture media, indicating that these chaperones contribute to robust and efficient filament formation. The ∆flgN ∆fliS ∆fliT (∆NST) cells produced short filaments similarly to the ∆fliS mutant. Suppressor mutations of the ∆NST cells, which lengthened the filament, were all found in FliC and destabilized the folded structure of FliC monomer. Deletion of FliS inhibited FliC export and filament elongation only after FliC synthesis was complete. We propose that FliS is not involved in the transport of FliC upon onset of filament formation, but FliS-assisted unfolding of FliC by the fT3SS becomes essential for its rapid and efficient export to form a long filament when FliC becomes fully expressed in the cytoplasm.
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Affiliation(s)
- Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, Suita, Japan
| | - Yusuke V Morimoto
- Department of Physics and Information Technology, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, Iizuka, Japan.,Japan Science and Technology Agency, PRESTO, Kawaguchi, Japan
| | - Miki Kinoshita
- Graduate School of Frontier Biosciences, Osaka University, Suita, Japan
| | - Keiichi Namba
- Graduate School of Frontier Biosciences, Osaka University, Suita, Japan.,RIKEN SPring-8 Center and Center for Biosystems Dynamics Research, Suita, Japan.,JEOL YOKOGUSHI Research Alliance Laboratories, Osaka University, Suita, Japan
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16
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Structural Dynamics of the Functional Nonameric Type III Translocase Export Gate. J Mol Biol 2021; 433:167188. [PMID: 34454944 DOI: 10.1016/j.jmb.2021.167188] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 07/30/2021] [Accepted: 08/02/2021] [Indexed: 11/20/2022]
Abstract
Type III protein secretion is widespread in Gram-negative pathogens. It comprises the injectisome with a surface-exposed needle and an inner membrane translocase. The translocase contains the SctRSTU export channel enveloped by the export gate subunit SctV that binds chaperone/exported clients and forms a putative ante-chamber. We probed the assembly, function, structure and dynamics of SctV from enteropathogenic E. coli (EPEC). In both EPEC and E. coli lab strains, SctV forms peripheral oligomeric clusters that are detergent-extracted as homo-nonamers. Membrane-embedded SctV9 is necessary and sufficient to act as a receptor for different chaperone/exported protein pairs with distinct C-domain binding sites that are essential for secretion. Negative staining electron microscopy revealed that peptidisc-reconstituted His-SctV9 forms a tripartite particle of ∼22 nm with a N-terminal domain connected by a short linker to a C-domain ring structure with a ∼5 nm-wide inner opening. The isolated C-domain ring was resolved with cryo-EM at 3.1 Å and structurally compared to other SctV homologues. Its four sub-domains undergo a three-stage "pinching" motion. Hydrogen-deuterium exchange mass spectrometry revealed this to involve dynamic and rigid hinges and a hyper-flexible sub-domain that flips out of the ring periphery and binds chaperones on and between adjacent protomers. These motions are coincident with local conformational changes at the pore surface and ring entry mouth that may also be modulated by the ATPase inner stalk. We propose that the intrinsic dynamics of the SctV protomer are modulated by chaperones and the ATPase and could affect allosterically the other subunits of the nonameric ring during secretion.
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17
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Guse A, Halte M, Hüsing S, Erhardt M. Hook-basal-body assembly state dictates substrate specificity of the flagellar type-III secretion system. Mol Microbiol 2021; 116:1189-1200. [PMID: 34467587 DOI: 10.1111/mmi.14805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 08/27/2021] [Accepted: 08/28/2021] [Indexed: 12/01/2022]
Abstract
The assembly of the bacterial flagellum is orchestrated by the secretion of distinct early and late secretion substrates via the flagellar-specific type-III secretion system (fT3SS). However, how the fT3SS is able to distinguish between the different (early and late) substrate classes during flagellar assembly remains poorly understood. In this study, we investigated the substrate selectivity and specificity of the fT3SS of Salmonella enterica at different assembly stages. For this, we developed an experimental setup that allowed us to synchronize hook-basal-body assembly and to monitor early and late substrate secretion of fT3SSs operating in either early or late secretion mode, respectively. Our results demonstrate that the fT3SS features a remarkable specificity for only the substrates required at the respective assembly stage. No crosstalk of substrates was observed for fT3SSs operating in the opposing secretion mode. We further found that a substantial fraction of fT3SS surprisingly remained in early secretion mode. Our results thus suggest that the secretion substrate specificity switch of the fT3SS is unidirectional and irreversible. The developed secretion substrate reporter system further provides a platform for future investigations of the underlying molecular mechanisms of the elusive substrate recognition of the T3SS.
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Affiliation(s)
- Alina Guse
- Institute for Biology, Humboldt-Universität zu Berlin, Berlin, Germany.,Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, USA
| | - Manuel Halte
- Institute for Biology, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Svenja Hüsing
- Institute for Biology, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Marc Erhardt
- Institute for Biology, Humboldt-Universität zu Berlin, Berlin, Germany.,Max Planck Unit for the Science of Pathogens, Berlin, Germany
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18
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Mitrović B, Lezerovich S, Sal-Man N. The Role of the Membrane-Associated Domain of the Export Apparatus Protein, EscV (SctV), in the Activity of the Type III Secretion System. Front Microbiol 2021; 12:719469. [PMID: 34413845 PMCID: PMC8369761 DOI: 10.3389/fmicb.2021.719469] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 07/05/2021] [Indexed: 11/13/2022] Open
Abstract
Diarrheal diseases remain a major public health concern worldwide. Many of the causative bacterial pathogens that cause these diseases have a specialized protein complex, the type III secretion system (T3SS), which delivers effector proteins directly into host cells. These effectors manipulate host cell processes for the benefit of the infecting bacteria. The T3SS structure resembles a syringe anchored within the bacterial membrane, projecting toward the host cell membrane. The entry port of the T3SS substrates, called the export apparatus, is formed by five integral membrane proteins. Among the export apparatus proteins, EscV is the largest, and as it forms a nonamer, it constitutes the largest portion of the export apparatus complex. While there are considerable data on the soluble cytoplasmic domain of EscV, our knowledge of its membrane-associated section and its transmembrane domains (TMDs) is still very limited. In this study, using an isolated genetic reporter system, we found that TMD5 and TMD6 of EscV mediate strong self-oligomerization. Substituting these TMDs within the full-length protein with a random hydrophobic sequence resulted in a complete loss of function of the T3SS, further suggesting that the EscV TMD5 and TMD6 sequences have a functional role in addition to their structural role as membrane anchors. As we observed only mild reduction in the ability of the TMD-exchanged variants to integrate into the full or intermediate T3SS complexes, we concluded that EscV TMD5 and TMD6 are not crucial for the global assembly or stability of the T3SS complex but are rather involved in promoting the necessary TMD–TMD interactions within the complex and the overall TMD orientation to allow channel opening for the entry of T3SS substrates.
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Affiliation(s)
- Boško Mitrović
- The Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beersheba, Israel
| | - Shir Lezerovich
- The Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beersheba, Israel
| | - Neta Sal-Man
- The Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beersheba, Israel
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19
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Bryant OJ, Chung BYW, Fraser GM. Chaperone-mediated coupling of subunit availability to activation of flagellar Type III secretion. Mol Microbiol 2021; 116:538-549. [PMID: 33893668 DOI: 10.1111/mmi.14731] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 04/19/2021] [Indexed: 01/07/2023]
Abstract
Bacterial flagellar subunits are exported across the cell membrane by the flagellar Type III Secretion System (fT3SS), powered by the proton motive force (pmf) and a specialized ATPase that enables the flagellar export gate to utilize the pmf electric potential (ΔΨ). Export gate activation is mediated by the ATPase stalk, FliJ, but how this process is regulated to prevent wasteful dissipation of pmf in the absence of subunit cargo is not known. Here, we show that FliJ activation of the export gate is regulated by flagellar export chaperones. FliJ binds unladen chaperones and, by using novel chaperone variants specifically defective for FliJ binding, we show that disruption of this interaction attenuates motility and cognate subunit export. We demonstrate in vitro that chaperones and the FlhA export gate component compete for binding to FliJ, and show in vivo that unladen chaperones, which would be present in the cell when subunit levels are low, sequester FliJ to prevent activation of the export gate and attenuate subunit export. Our data indicate a mechanism whereby chaperones couple availability of subunit cargo to pmf-driven export by the fT3SS.
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Affiliation(s)
- Owain J Bryant
- Department of Pathology, University of Cambridge, Cambridge, UK
| | - Betty Y-W Chung
- Department of Pathology, University of Cambridge, Cambridge, UK
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20
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Bacterial Flagellar Filament: A Supramolecular Multifunctional Nanostructure. Int J Mol Sci 2021; 22:ijms22147521. [PMID: 34299141 PMCID: PMC8306008 DOI: 10.3390/ijms22147521] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 07/06/2021] [Accepted: 07/10/2021] [Indexed: 02/07/2023] Open
Abstract
The bacterial flagellum is a complex and dynamic nanomachine that propels bacteria through liquids. It consists of a basal body, a hook, and a long filament. The flagellar filament is composed of thousands of copies of the protein flagellin (FliC) arranged helically and ending with a filament cap composed of an oligomer of the protein FliD. The overall structure of the filament core is preserved across bacterial species, while the outer domains exhibit high variability, and in some cases are even completely absent. Flagellar assembly is a complex and energetically costly process triggered by environmental stimuli and, accordingly, highly regulated on transcriptional, translational and post-translational levels. Apart from its role in locomotion, the filament is critically important in several other aspects of bacterial survival, reproduction and pathogenicity, such as adhesion to surfaces, secretion of virulence factors and formation of biofilms. Additionally, due to its ability to provoke potent immune responses, flagellins have a role as adjuvants in vaccine development. In this review, we summarize the latest knowledge on the structure of flagellins, capping proteins and filaments, as well as their regulation and role during the colonization and infection of the host.
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21
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Minamino T, Morimoto YV, Kinoshita M, Namba K. Membrane voltage-dependent activation mechanism of the bacterial flagellar protein export apparatus. Proc Natl Acad Sci U S A 2021; 118:e2026587118. [PMID: 34035173 PMCID: PMC8179193 DOI: 10.1073/pnas.2026587118] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The proton motive force (PMF) consists of the electric potential difference (Δψ), which is measured as membrane voltage, and the proton concentration difference (ΔpH) across the cytoplasmic membrane. The flagellar protein export machinery is composed of a PMF-driven transmembrane export gate complex and a cytoplasmic ATPase ring complex consisting of FliH, FliI, and FliJ. ATP hydrolysis by the FliI ATPase activates the export gate complex to become an active protein transporter utilizing Δψ to drive proton-coupled protein export. An interaction between FliJ and a transmembrane ion channel protein, FlhA, is a critical step for Δψ-driven protein export. To clarify how Δψ is utilized for flagellar protein export, we analyzed the export properties of the export gate complex in the absence of FliH and FliI. The protein transport activity of the export gate complex was very low at external pH 7.0 but increased significantly with an increase in Δψ by an upward shift of external pH from 7.0 to 8.5. This observation suggests that the export gate complex is equipped with a voltage-gated mechanism. An increase in the cytoplasmic level of FliJ and a gain-of-function mutation in FlhA significantly reduced the Δψ dependency of flagellar protein export by the export gate complex. However, deletion of FliJ decreased Δψ-dependent protein export significantly. We propose that Δψ is required for efficient interaction between FliJ and FlhA to open the FlhA ion channel to conduct protons to drive flagellar protein export in a Δψ-dependent manner.
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Affiliation(s)
- Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, Osaka 565-0871, Japan;
| | - Yusuke V Morimoto
- Department of Physics and Information Technology, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, Fukuoka 820-8502, Japan
- Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Kawaguchi 332-0012, Japan
| | - Miki Kinoshita
- Graduate School of Frontier Biosciences, Osaka University, Osaka 565-0871, Japan
| | - Keiichi Namba
- Graduate School of Frontier Biosciences, Osaka University, Osaka 565-0871, Japan;
- SPring-8 Center, RIKEN, Osaka 565-0871, Japan
- Center for Biosystems Dynamics Research, RIKEN, Osaka 565-0871, Japan
- JEOL YOKOGUSHI Research Alliance Laboratories, Osaka University, Osaka 565-0871, Japan
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22
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Inoue Y, Kinoshita M, Kida M, Takekawa N, Namba K, Imada K, Minamino T. The FlhA linker mediates flagellar protein export switching during flagellar assembly. Commun Biol 2021; 4:646. [PMID: 34059784 PMCID: PMC8166844 DOI: 10.1038/s42003-021-02177-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Accepted: 05/04/2021] [Indexed: 12/15/2022] Open
Abstract
The flagellar protein export apparatus switches substrate specificity from hook-type to filament-type upon hook assembly completion, thereby initiating filament assembly at the hook tip. The C-terminal cytoplasmic domain of FlhA (FlhAC) serves as a docking platform for flagellar chaperones in complex with their cognate filament-type substrates. Interactions of the flexible linker of FlhA (FlhAL) with its nearest FlhAC subunit in the FlhAC ring is required for the substrate specificity switching. To address how FlhAL brings the order to flagellar assembly, we analyzed the flhA(E351A/W354A/D356A) ΔflgM mutant and found that this triple mutation in FlhAL increased the secretion level of hook protein by 5-fold, thereby increasing hook length. The crystal structure of FlhAC(E351A/D356A) showed that FlhAL bound to the chaperone-binding site of its neighboring subunit. We propose that the interaction of FlhAL with the chaperon-binding site of FlhAC suppresses filament-type protein export and facilitates hook-type protein export during hook assembly.
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Affiliation(s)
- Yumi Inoue
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan.,Department of Ophthalmology and Visual Sciences, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Miki Kinoshita
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
| | - Mamoru Kida
- Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan
| | - Norihiro Takekawa
- Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan
| | - Keiichi Namba
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan.,RIKEN SPring-8 Center and Center for Biosystems Dynamics Research, Suita, Osaka, Japan.,JEOL YOKOGUSHI Research Alliance Laboratories, Osaka University, Suita, Osaka, Japan
| | - Katsumi Imada
- Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan.
| | - Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan.
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23
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Kinoshita M, Namba K, Minamino T. A positive charge region of Salmonella FliI is required for ATPase formation and efficient flagellar protein export. Commun Biol 2021; 4:464. [PMID: 33846530 PMCID: PMC8041783 DOI: 10.1038/s42003-021-01980-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 03/12/2021] [Indexed: 01/28/2023] Open
Abstract
The FliH2FliI complex is thought to pilot flagellar subunit proteins from the cytoplasm to the transmembrane export gate complex for flagellar assembly in Salmonella enterica. FliI also forms a homo-hexamer to hydrolyze ATP, thereby activating the export gate complex to become an active protein transporter. However, it remains unknown how this activation occurs. Here we report the role of a positively charged cluster formed by Arg-26, Arg-27, Arg-33, Arg-76 and Arg-93 of FliI in flagellar protein export. We show that Arg-33 and Arg-76 are involved in FliI ring formation and that the fliI(R26A/R27A/R33A/R76A/R93A) mutant requires the presence of FliH to fully exert its export function. We observed that gain-of-function mutations in FlhB increased the probability of substrate entry into the export gate complex, thereby restoring the export function of the ∆fliH fliI(R26A/R27A/R33A/R76A/R93A) mutant. We suggest that the positive charge cluster of FliI is responsible not only for well-regulated hexamer assembly but also for substrate entry into the gate complex. Kinoshita, Namba and Minamino show that a cluster of positively-charged arginines in the Salmonella FliI is necessary for formation of the FliI homo-hexamer ATPase. Through loss- and gain-of-function experiments, they demonstrate that hexamer assembly is also responsible for efficient export of flagellar proteins during flagellar assembly.
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Affiliation(s)
- Miki Kinoshita
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
| | - Keiichi Namba
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan.,RIKEN SPring-8 Center and Center for Biosystems Dynamics Research, Suita, Osaka, Japan.,JEOL YOKOGUSHI Research Alliance Laboratories, Osaka University, Suita, Osaka, Japan
| | - Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan.
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24
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Role of DegQ in differential stability of flagellin subunits in Vibrio vulnificus. NPJ Biofilms Microbiomes 2021; 7:32. [PMID: 33833236 PMCID: PMC8032703 DOI: 10.1038/s41522-021-00206-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 03/12/2021] [Indexed: 12/29/2022] Open
Abstract
Biofilm formation of Vibrio vulnificus is initiated by adherence of flagellated cells to surfaces, and then flagellum-driven motility is not necessary during biofilm maturation. Once matured biofilms are constructed, cells become flagellated and swim to disperse from biofilms. As a consequence, timely regulations of the flagellar components’ expression are crucial to complete a biofilm life-cycle. In this study, we demonstrated that flagellins’ production is regulated in a biofilm stage-specific manner, via activities of a protease DegQ and a chaperone FlaJ. Among four flagellin subunits for V. vulnificus filament, FlaC had the highest affinities to hook-associated proteins, and is critical for maturating flagellum, showed the least susceptibility to DegQ due to the presence of methionine residues in its DegQ-sensitive domains, ND1 and CD0. Therefore, differential regulation by DegQ and FlaJ controls the cytoplasmic stability of flagellins, which further determines the motility-dependent, stage-specific development of biofilms.
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25
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Bouteiller M, Dupont C, Bourigault Y, Latour X, Barbey C, Konto-Ghiorghi Y, Merieau A. Pseudomonas Flagella: Generalities and Specificities. Int J Mol Sci 2021; 22:ijms22073337. [PMID: 33805191 PMCID: PMC8036289 DOI: 10.3390/ijms22073337] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 03/22/2021] [Accepted: 03/22/2021] [Indexed: 12/21/2022] Open
Abstract
Flagella-driven motility is an important trait for bacterial colonization and virulence. Flagella rotate and propel bacteria in liquid or semi-liquid media to ensure such bacterial fitness. Bacterial flagella are composed of three parts: a membrane complex, a flexible-hook, and a flagellin filament. The most widely studied models in terms of the flagellar apparatus are E. coli and Salmonella. However, there are many differences between these enteric bacteria and the bacteria of the Pseudomonas genus. Enteric bacteria possess peritrichous flagella, in contrast to Pseudomonads, which possess polar flagella. In addition, flagellar gene expression in Pseudomonas is under a four-tiered regulatory circuit, whereas enteric bacteria express flagellar genes in a three-step manner. Here, we use knowledge of E. coli and Salmonella flagella to describe the general properties of flagella and then focus on the specificities of Pseudomonas flagella. After a description of flagellar structure, which is highly conserved among Gram-negative bacteria, we focus on the steps of flagellar assembly that differ between enteric and polar-flagellated bacteria. In addition, we summarize generalities concerning the fuel used for the production and rotation of the flagellar macromolecular complex. The last part summarizes known regulatory pathways and potential links with the type-six secretion system (T6SS).
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Affiliation(s)
- Mathilde Bouteiller
- LMSM, Laboratoire de Microbiologie Signaux et Microenvironnement, EA 4312, Normandy University, Université de Rouen, 27000 Evreux, France; (M.B.); (C.D.); (Y.B.); (X.L.); (C.B.); (Y.K.-G.)
- SFR NORVEGE, Structure Fédérative de Recherche Normandie Végétale, FED 4277, 76821 Mont-Saint-Aignan, France
| | - Charly Dupont
- LMSM, Laboratoire de Microbiologie Signaux et Microenvironnement, EA 4312, Normandy University, Université de Rouen, 27000 Evreux, France; (M.B.); (C.D.); (Y.B.); (X.L.); (C.B.); (Y.K.-G.)
- SFR NORVEGE, Structure Fédérative de Recherche Normandie Végétale, FED 4277, 76821 Mont-Saint-Aignan, France
| | - Yvann Bourigault
- LMSM, Laboratoire de Microbiologie Signaux et Microenvironnement, EA 4312, Normandy University, Université de Rouen, 27000 Evreux, France; (M.B.); (C.D.); (Y.B.); (X.L.); (C.B.); (Y.K.-G.)
- SFR NORVEGE, Structure Fédérative de Recherche Normandie Végétale, FED 4277, 76821 Mont-Saint-Aignan, France
| | - Xavier Latour
- LMSM, Laboratoire de Microbiologie Signaux et Microenvironnement, EA 4312, Normandy University, Université de Rouen, 27000 Evreux, France; (M.B.); (C.D.); (Y.B.); (X.L.); (C.B.); (Y.K.-G.)
- SFR NORVEGE, Structure Fédérative de Recherche Normandie Végétale, FED 4277, 76821 Mont-Saint-Aignan, France
| | - Corinne Barbey
- LMSM, Laboratoire de Microbiologie Signaux et Microenvironnement, EA 4312, Normandy University, Université de Rouen, 27000 Evreux, France; (M.B.); (C.D.); (Y.B.); (X.L.); (C.B.); (Y.K.-G.)
- SFR NORVEGE, Structure Fédérative de Recherche Normandie Végétale, FED 4277, 76821 Mont-Saint-Aignan, France
| | - Yoan Konto-Ghiorghi
- LMSM, Laboratoire de Microbiologie Signaux et Microenvironnement, EA 4312, Normandy University, Université de Rouen, 27000 Evreux, France; (M.B.); (C.D.); (Y.B.); (X.L.); (C.B.); (Y.K.-G.)
- SFR NORVEGE, Structure Fédérative de Recherche Normandie Végétale, FED 4277, 76821 Mont-Saint-Aignan, France
| | - Annabelle Merieau
- LMSM, Laboratoire de Microbiologie Signaux et Microenvironnement, EA 4312, Normandy University, Université de Rouen, 27000 Evreux, France; (M.B.); (C.D.); (Y.B.); (X.L.); (C.B.); (Y.K.-G.)
- SFR NORVEGE, Structure Fédérative de Recherche Normandie Végétale, FED 4277, 76821 Mont-Saint-Aignan, France
- Correspondence:
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26
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The FlgN chaperone activates the Na +-driven engine of the Salmonella flagellar protein export apparatus. Commun Biol 2021; 4:335. [PMID: 33712678 PMCID: PMC7955116 DOI: 10.1038/s42003-021-01865-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Accepted: 02/17/2021] [Indexed: 01/13/2023] Open
Abstract
The bacterial flagellar protein export machinery consists of a transmembrane export gate complex and a cytoplasmic ATPase complex. The gate complex has two intrinsic and distinct H+-driven and Na+-driven engines to drive the export of flagellar structural proteins. Salmonella wild-type cells preferentially use the H+-driven engine under a variety of environmental conditions. To address how the Na+-driven engine is activated, we analyzed the fliJ(Δ13–24) fliH(Δ96–97) mutant and found that the interaction of the FlgN chaperone with FlhA activates the Na+-driven engine when the ATPase complex becomes non-functional. A similar activation can be observed with either of two single-residue substitutions in FlhA. Thus, it is likely that the FlgN-FlhA interaction generates a conformational change in FlhA that allows it to function as a Na+ channel. We propose that this type of activation would be useful for flagellar construction under conditions in which the proton motive force is severely restricted. Minamino et al. report that the bacterial FlgN chaperone acts as a switch to activate a backup mechanism for H+-coupled flagellar protein export by interacting with FlhAC to activate the Na+-driven export engine. The proposed mechanism helps to explain how bacteria can maintain flagellar protein export when the ATPase complex export machinery becomes non-functional.
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27
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Morimoto YV, Minamino T. Architecture and Assembly of the Bacterial Flagellar Motor Complex. Subcell Biochem 2021; 96:297-321. [PMID: 33252734 DOI: 10.1007/978-3-030-58971-4_8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
One of the central systems responsible for bacterial motility is the flagellum. The bacterial flagellum is a macromolecular protein complex that is more than five times the cell length. Flagella-driven motility is coordinated via a chemosensory signal transduction pathway, and so bacterial cells sense changes in the environment and migrate towards more desirable locations. The flagellum of Salmonella enterica serovar Typhimurium is composed of a bi-directional rotary motor, a universal joint and a helical propeller. The flagellar motor, which structurally resembles an artificial motor, is embedded within the cell envelop and spins at several hundred revolutions per second. In contrast to an artificial motor, the energy utilized for high-speed flagellar motor rotation is the inward-directed proton flow through a transmembrane proton channel of the stator unit of the flagellar motor. The flagellar motor realizes efficient chemotaxis while performing high-speed movement by an ingenious directional switching mechanism of the motor rotation. To build the universal joint and helical propeller structures outside the cell body, the flagellar motor contains its own protein transporter called a type III protein export apparatus. In this chapter we summarize the structure and assembly of the Salmonella flagellar motor complex.
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Affiliation(s)
- Yusuke V Morimoto
- Department of Physics and Information Technology, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, 680-4 Kawazu, Iizuka, Fukuoka, 820-8502, Japan
| | - Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan.
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28
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Protein Export via the Type III Secretion System of the Bacterial Flagellum. Biomolecules 2021; 11:biom11020186. [PMID: 33572887 PMCID: PMC7911332 DOI: 10.3390/biom11020186] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 01/25/2021] [Accepted: 01/26/2021] [Indexed: 12/15/2022] Open
Abstract
The bacterial flagellum and the related virulence-associated injectisome system of pathogenic bacteria utilize a type III secretion system (T3SS) to export substrate proteins across the inner membrane in a proton motive force-dependent manner. The T3SS is composed of an export gate (FliPQR/FlhA/FlhB) located in the flagellar basal body and an associated soluble ATPase complex in the cytoplasm (FliHIJ). Here, we summarise recent insights into the structure, assembly and protein secretion mechanisms of the T3SS with a focus on energy transduction and protein transport across the cytoplasmic membrane.
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29
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Hook JC, Blagotinsek V, Pané-Farré J, Mrusek D, Altegoer F, Dornes A, Schwan M, Schier L, Thormann KM, Bange G. A Proline-Rich Element in the Type III Secretion Protein FlhB Contributes to Flagellar Biogenesis in the Beta- and Gamma-Proteobacteria. Front Microbiol 2020; 11:564161. [PMID: 33384667 PMCID: PMC7771051 DOI: 10.3389/fmicb.2020.564161] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 10/26/2020] [Indexed: 11/24/2022] Open
Abstract
Flagella are bacterial organelles of locomotion. Their biogenesis is highly coordinated in time and space and relies on a specialized flagellar type III secretion system (fT3SS) required for the assembly of the extracellular hook, rod, and filament parts of this complex motor device. The fT3SS protein FlhB switches secretion substrate specificity once the growing hook reaches its determined length. Here we present the crystal structure of the cytoplasmic domain of the transmembrane protein FlhB. The structure visualizes a so-far unseen proline-rich region (PRR) at the very C-terminus of the protein. Strains lacking the PRR show a decrease in flagellation as determined by hook- and filament staining, indicating a role of the PRR during assembly of the hook and filament structures. Phylogenetic analysis shows that the PRR is a primary feature of FlhB proteins of flagellated beta- and gamma-proteobacteria. Taken together, our study adds another layer of complexity and organismic diversity to the process of flagella biogenesis.
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Affiliation(s)
- John C Hook
- Department of Microbiology and Molecular Biology, Justus-Liebig-Universität, Giessen, Germany
| | - Vitan Blagotinsek
- SYNMIKRO Research Center, Department of Chemistry, Philipps-University Marburg, Marburg, Germany
| | - Jan Pané-Farré
- SYNMIKRO Research Center, Department of Chemistry, Philipps-University Marburg, Marburg, Germany
| | - Devid Mrusek
- SYNMIKRO Research Center, Department of Chemistry, Philipps-University Marburg, Marburg, Germany
| | - Florian Altegoer
- SYNMIKRO Research Center, Department of Chemistry, Philipps-University Marburg, Marburg, Germany
| | - Anita Dornes
- SYNMIKRO Research Center, Department of Chemistry, Philipps-University Marburg, Marburg, Germany
| | - Meike Schwan
- Department of Microbiology and Molecular Biology, Justus-Liebig-Universität, Giessen, Germany
| | - Lukas Schier
- SYNMIKRO Research Center, Department of Chemistry, Philipps-University Marburg, Marburg, Germany
| | - Kai M Thormann
- Department of Microbiology and Molecular Biology, Justus-Liebig-Universität, Giessen, Germany
| | - Gert Bange
- SYNMIKRO Research Center, Department of Chemistry, Philipps-University Marburg, Marburg, Germany
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30
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Zhuang XY, Lo CJ. Construction and Loss of Bacterial Flagellar Filaments. Biomolecules 2020; 10:E1528. [PMID: 33182435 PMCID: PMC7696725 DOI: 10.3390/biom10111528] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 10/26/2020] [Accepted: 11/04/2020] [Indexed: 11/16/2022] Open
Abstract
The bacterial flagellar filament is an extracellular tubular protein structure that acts as a propeller for bacterial swimming motility. It is connected to the membrane-anchored rotary bacterial flagellar motor through a short hook. The bacterial flagellar filament consists of approximately 20,000 flagellins and can be several micrometers long. In this article, we reviewed the experimental works and models of flagellar filament construction and the recent findings of flagellar filament ejection during the cell cycle. The length-dependent decay of flagellar filament growth data supports the injection-diffusion model. The decay of flagellar growth rate is due to reduced transportation of long-distance diffusion and jamming. However, the filament is not a permeant structure. Several bacterial species actively abandon their flagella under starvation. Flagellum is disassembled when the rod is broken, resulting in an ejection of the filament with a partial rod and hook. The inner membrane component is then diffused on the membrane before further breakdown. These new findings open a new field of bacterial macro-molecule assembly, disassembly, and signal transduction.
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Affiliation(s)
| | - Chien-Jung Lo
- Department of Physics and Graduate Institute of Biophysics, National Central University, Taoyuan City 32001, Taiwan;
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31
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The flexible linker of the secreted FliK ruler is required for export switching of the flagellar protein export apparatus. Sci Rep 2020; 10:838. [PMID: 31964971 PMCID: PMC6972891 DOI: 10.1038/s41598-020-57782-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Accepted: 01/02/2020] [Indexed: 12/19/2022] Open
Abstract
The hook length of the flagellum is controlled to about 55 nm in Salmonella. The flagellar type III protein export apparatus secretes FliK to determine hook length during hook assembly and changes its substrate specificity from the hook protein to the filament protein when the hook length has reached about 55 nm. Salmonella FliK consists of an N-terminal domain (FliKN, residues 1–207), a C-terminal domain (FliKC, residues 268–405) and a flexible linker (FliKL, residues 208–267) connecting these two domains. FliKN is a ruler to measure hook length. FliKC binds to a transmembrane export gate protein FlhB to undergo the export switching. FliKL not only acts as part of the ruler but also contributes to this switching event, but it remains unknown how. Here we report that FliKL is required for efficient interaction of FliKC with FlhB. Deletions in FliKL not only shortened hook length according to the size of deletions but also caused a loose length control. Deletion of residues 206–265 significantly reduced the binding affinity of FliKC for FlhB, thereby producing much longer hooks. We propose that an appropriate length of FliKL is required for efficient interaction of FliKC with FlhB.
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32
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FliK-Driven Conformational Rearrangements of FlhA and FlhB Are Required for Export Switching of the Flagellar Protein Export Apparatus. J Bacteriol 2020; 202:JB.00637-19. [PMID: 31712281 DOI: 10.1128/jb.00637-19] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Accepted: 11/06/2019] [Indexed: 12/31/2022] Open
Abstract
FlhA and FlhB are transmembrane proteins of the flagellar type III protein export apparatus, and their C-terminal cytoplasmic domains (FlhAC and FlhBC) coordinate flagellar protein export with assembly. FlhBC undergoes autocleavage between Asn-269 and Pro-270 in a well-conserved NPTH loop located between FlhBCN and FlhBCC polypeptides and interacts with the C-terminal domain of the FliK ruler when the length of the hook has reached about 55 nm in Salmonella As a result, the flagellar protein export apparatus switches its substrate specificity, thereby terminating hook assembly and initiating filament assembly. The mechanism of export switching remains unclear. Here, we report the role of FlhBC cleavage in the switching mechanism. Photo-cross-linking experiments revealed that the flhB(N269A) and flhB(P270A) mutations did not affect the binding affinity of FlhBC for FliK. Genetic analysis of the flhB(P270A) mutant revealed that the P270A mutation affects a FliK-dependent conformational change of FlhBC, thereby inhibiting the substrate specificity switching. The flhA(A489E) mutation in FlhAC suppressed the flhB(P270A) mutation, suggesting that an interaction between FlhBC and FlhAC is critical for the export switching. We propose that the interaction between FliKC and a cleaved form of FlhBC promotes a conformational change in FlhBC responsible for the termination of hook-type protein export and a structural remodeling of the FlhAC ring responsible for the initiation of filament-type protein export.IMPORTANCE The flagellar type III protein export apparatus coordinates protein export with assembly, which allows the flagellum to be efficiently built at the cell surface. Hook completion is an important morphological checkpoint for the sequential flagellar assembly process. The protein export apparatus switches its substrate specificity from the hook protein to the filament protein upon hook completion. FliK, FlhB, and FlhA are involved in the export-switching process, but the mechanism remains a mystery. By analyzing a slow-cleaving flhB(P270A) mutant, we provide evidence that an interaction between FliK and FlhB induces conformational rearrangements in FlhB, followed by a structural remodeling of the FlhA ring structure that terminates hook assembly and initiates filament formation.
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33
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In Vitro Autonomous Construction of the Flagellar Axial Structure in Inverted Membrane Vesicles. Biomolecules 2020; 10:biom10010126. [PMID: 31940802 PMCID: PMC7022808 DOI: 10.3390/biom10010126] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 01/08/2020] [Accepted: 01/09/2020] [Indexed: 02/07/2023] Open
Abstract
The bacterial flagellum is a filamentous organelle extending from the cell surface. The axial structure of the flagellum consists of the rod, hook, junction, filament, and cap. The axial structure is formed by axial component proteins exported via a specific protein export apparatus in a well-regulated manner. Although previous studies have revealed the outline of the flagellar construction process, the mechanism of axial structure formation, including axial protein export, is still obscure due to difficulties in direct observation of protein export and assembly in vivo. We recently developed an in vitro flagellar protein transport assay system using inverted membrane vesicles (IMVs) and succeeded in reproducing the early stage of flagellar assembly. However, the late stage of the flagellar formation process remained to be examined in the IMVs. In this study, we showed that the filament-type proteins are transported into the IMVs to produce the filament on the hook inside the IMVs. Furthermore, we provide direct evidence that coordinated flagellar protein export and assembly can occur at the post-translational level. These results indicate that the ordered construction of the entire flagellar structure can be regulated by only the interactions between the protein export apparatus, the export substrate proteins, and their cognate chaperones.
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34
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Inoue Y, Kinoshita M, Namba K, Minamino T. Mutational analysis of the C-terminal cytoplasmic domain of FlhB, a transmembrane component of the flagellar type III protein export apparatus in Salmonella. Genes Cells 2019; 24:408-421. [PMID: 30963674 DOI: 10.1111/gtc.12684] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Revised: 04/01/2019] [Accepted: 04/02/2019] [Indexed: 11/27/2022]
Abstract
The flagellar protein export apparatus switches its substrate specificity when hook length has reached approximately 55 nm in Salmonella. The C-terminal cytoplasmic domain of FlhB (FlhBC ) is involved in this switching process. FlhBC consists of FlhBCN and FlhBCC polypeptides. FlhBCC has a flexible C-terminal tail (FlhBCCT ). FlhBCC is involved in substrate recognition, and conformational rearrangements of FlhBCN -FlhBCC boundary are postulated to be required for the export switching. However, it remains unknown how it occurs. To clarify this question, we carried out mutational analysis of highly conserved residues in FlhBC . The flhB(E230A) mutation reduced the FlhB function. The flhB(E11S) mutation restored the protein transport activity of the flhB(E230A) mutant to the wild-type level, suggesting that the interaction of FlhBCN with the extreme N-terminal region of FlhB is required for flagellar protein export. The flhB(R320A) mutation affected hydrophobic interaction networks in FlhBCC , thereby increasing insolubility of FlhBC . The R320A mutation also affected the export switching, thereby producing longer hooks with the filament attached. C-terminal truncations of FlhBCCT induced a conformational change of FlhBCN -FlhBCC boundary, resulting in a loose hook length control. We propose that FlhBCCT may control conformational arrangements of FlhBCN -FlhBCC boundary through the hydrophobic interaction networks of FlhBCC .
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Affiliation(s)
- Yumi Inoue
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
| | - Miki Kinoshita
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
| | - Keiichi Namba
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan.,RIKEN Center for Biosystems Dynamic Research & Spring-8 Center, Suita, Osaka, Japan
| | - Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
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35
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Inoue Y, Ogawa Y, Kinoshita M, Terahara N, Shimada M, Kodera N, Ando T, Namba K, Kitao A, Imada K, Minamino T. Structural Insights into the Substrate Specificity Switch Mechanism of the Type III Protein Export Apparatus. Structure 2019; 27:965-976.e6. [PMID: 31031200 DOI: 10.1016/j.str.2019.03.017] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 01/16/2019] [Accepted: 03/22/2019] [Indexed: 12/22/2022]
Abstract
Bacteria use a type III protein export apparatus for construction of the flagellum, which consists of the basal body, the hook, and the filament. FlhA forms a homo-nonamer through its C-terminal cytoplasmic domains (FlhAC) and ensures the strict order of flagellar assembly. FlhAC goes through dynamic domain motions during protein export, but it remains unknown how it occurs. Here, we report that the FlhA(G368C) mutation biases FlhAC toward a closed form, thereby reducing the binding affinity of FlhAC for flagellar export chaperones in complex with their cognate filament-type substrates. The G368C mutations also restrict the conformational flexibility of a linker region of FlhA (FlhAL), suppressing FlhAC ring formation. We propose that interactions of FlhAL with its neighboring subunit converts FlhAC in the ring from a closed conformation to an open one, allowing the chaperon/substrate complexes to bind to the FlhAC ring to form the filament at the hook tip.
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Affiliation(s)
- Yumi Inoue
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Yuya Ogawa
- Department of Macromolecular Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan
| | - Miki Kinoshita
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Naoya Terahara
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Masafumi Shimada
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Noriyuki Kodera
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | - Toshio Ando
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | - Keiichi Namba
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan; RIKEN Center for Biosystems Dynamics Research & SPring-8 Center, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Akio Kitao
- School of Life Science and Technology, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8550, Japan.
| | - Katsumi Imada
- Department of Macromolecular Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan.
| | - Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan.
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Molecular Organization and Assembly of the Export Apparatus of Flagellar Type III Secretion Systems. Curr Top Microbiol Immunol 2019; 427:91-107. [PMID: 31172377 DOI: 10.1007/82_2019_170] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The bacterial flagellum is a supramolecular motility machine consisting of the basal body, the hook, and the filament. For construction of the flagellum beyond the cellular membranes, a type III protein export apparatus uses ATP and proton-motive force (PMF) across the cytoplasmic membrane as the energy sources to transport flagellar component proteins from the cytoplasm to the distal end of the growing flagellar structure. The protein export apparatus consists of a PMF-driven transmembrane export gate complex and a cytoplasmic ATPase complex. In addition, the basal body C ring acts as a sorting platform for the cytoplasmic ATPase complex that efficiently brings export substrates and type III export chaperone-substrate complexes from the cytoplasm to the export gate complex. In this book chapter, we will summarize our current understanding of molecular organization and assembly of the flagellar type III protein export apparatus.
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37
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Export Mechanisms and Energy Transduction in Type-III Secretion Machines. Curr Top Microbiol Immunol 2019; 427:143-159. [PMID: 31218506 DOI: 10.1007/82_2019_166] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The remarkably complex architecture and organization of bacterial nanomachines originally raised the enigma to how they are assembled in a coordinated manner. Over the years, the assembly processes of the flagellum and evolutionary-related injectisome complexes have been deciphered and were shown to rely on a conserved protein secretion machine: the type-III secretion system. In this book chapter, we demonstrate how individually evolved mechanisms cooperate in highly versatile and robust secretion machinery to export and assemble the building blocks of those nanomachines.
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Altegoer F, Mukherjee S, Steinchen W, Bedrunka P, Linne U, Kearns DB, Bange G. FliS/flagellin/FliW heterotrimer couples type III secretion and flagellin homeostasis. Sci Rep 2018; 8:11552. [PMID: 30068950 PMCID: PMC6070490 DOI: 10.1038/s41598-018-29884-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Accepted: 07/20/2018] [Indexed: 01/08/2023] Open
Abstract
Flagellin is amongst the most abundant proteins in flagellated bacterial species and constitutes the major building block of the flagellar filament. The proteins FliW and FliS serve in the post-transcriptional control of flagellin and guide the protein to the flagellar type III secretion system (fT3SS), respectively. Here, we present the high-resolution structure of FliS/flagellin heterodimer and show that FliS and FliW bind to opposing interfaces located at the N- and C-termini of flagellin. The FliS/flagellin/FliW heterotrimer is able to interact with FlhA-C suggesting that FliW and FliS are released during flagellin export. After release, FliW and FliS are recycled to execute a new round of post-transcriptional regulation and targeting. Taken together, our study provides a mechanism explaining how FliW and FliS synchronize the production of flagellin with the capacity of the fT3SS to secrete flagellin.
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Affiliation(s)
- Florian Altegoer
- LOEWE Center for Synthetic Microbiology & Dep. of Chemistry, Philipps University Marburg, Hans-Meerwein-Strasse 6, 35043, Marburg, Germany
| | - Sampriti Mukherjee
- Department of Biology, Indiana University, 1001 East 3rd Street, Bloomington, IN, 47405, USA
| | - Wieland Steinchen
- LOEWE Center for Synthetic Microbiology & Dep. of Chemistry, Philipps University Marburg, Hans-Meerwein-Strasse 6, 35043, Marburg, Germany
| | - Patricia Bedrunka
- LOEWE Center for Synthetic Microbiology & Dep. of Chemistry, Philipps University Marburg, Hans-Meerwein-Strasse 6, 35043, Marburg, Germany
| | - Uwe Linne
- LOEWE Center for Synthetic Microbiology & Dep. of Chemistry, Philipps University Marburg, Hans-Meerwein-Strasse 6, 35043, Marburg, Germany
| | - Daniel B Kearns
- Department of Biology, Indiana University, 1001 East 3rd Street, Bloomington, IN, 47405, USA
| | - Gert Bange
- LOEWE Center for Synthetic Microbiology & Dep. of Chemistry, Philipps University Marburg, Hans-Meerwein-Strasse 6, 35043, Marburg, Germany.
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In Vitro
Reconstitution of Functional Type III Protein Export and Insights into Flagellar Assembly. mBio 2018; 9:mBio.00988-18. [PMID: 29946050 PMCID: PMC6020293 DOI: 10.1128/mbio.00988-18] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
ABSTRACT
The type III secretion system (T3SS) forms the functional core of injectisomes, protein transporters that allow bacteria to deliver virulence factors into their hosts for infection, and flagella, which are critical for many pathogens to reach the site of infection. In spite of intensive genetic and biochemical studies, the T3SS protein export mechanism remains unclear due to the difficulty of accurate measurement of protein export
in vivo
. Here, we developed an
in vitro
flagellar T3S protein transport assay system using an inverted cytoplasmic membrane vesicle (IMV) for accurate and controlled measurements of flagellar protein export. We show that the flagellar T3SS in the IMV fully retains export activity. The flagellar hook was constructed inside the lumen of the IMV by adding purified component proteins externally to the IMV solution. We reproduced the hook length control and export specificity switch in the IMV consistent with that seen in the native cell. Previous
in vivo
analyses showed that flagellar protein export is driven by proton motive force (PMF) and facilitated by ATP hydrolysis by FliI, a T3SS-specific ATPase. Our
in vitro
assay recapitulated these previous
in vivo
observations but furthermore clearly demonstrated that even ATP hydrolysis by FliI alone can drive flagellar protein export. Moreover, this assay showed that addition of the FliH
2
/FliI complex to the assay solution at a concentration similar to that in the cell dramatically enhanced protein export, confirming that the FliH
2
/FliI complex in the cytoplasm is important for effective protein transport.
IMPORTANCE
The type III secretion system (T3SS) is the functional core of the injectisome, a bacterial protein transporter used to deliver virulence proteins into host cells, and bacterial flagella, critical for many pathogens. The molecular mechanism of protein transport is still unclear due to difficulties in accurate measurements of protein transport under well-controlled conditions
in vivo
. We succeeded in developing an
in vitro
transport assay system of the flagellar T3SS using inverted membrane vesicles (IMVs). Flagellar hook formation was reproduced in the IMV, suggesting that the export apparatus in the IMV retains a protein transport activity similar to that in the cell. Using this system, we revealed that ATP hydrolysis by the T3SS ATPase can drive protein export without PMF.
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40
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Minamino T. Hierarchical protein export mechanism of the bacterial flagellar type III protein export apparatus. FEMS Microbiol Lett 2018; 365:4993518. [DOI: 10.1093/femsle/fny117] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 05/04/2018] [Indexed: 12/18/2022] Open
Affiliation(s)
- Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
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41
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Xing Q, Shi K, Portaliou A, Rossi P, Economou A, Kalodimos CG. Structures of chaperone-substrate complexes docked onto the export gate in a type III secretion system. Nat Commun 2018; 9:1773. [PMID: 29720631 PMCID: PMC5932034 DOI: 10.1038/s41467-018-04137-4] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 04/05/2018] [Indexed: 12/31/2022] Open
Abstract
The flagellum and the injectisome enable bacterial locomotion and pathogenesis, respectively. These nanomachines assemble and function using a type III secretion system (T3SS). Exported proteins are delivered to the export apparatus by dedicated cytoplasmic chaperones for their transport through the membrane. The structural and mechanistic basis of this process is poorly understood. Here we report the structures of two ternary complexes among flagellar chaperones (FliT and FliS), protein substrates (the filament-capping FliD and flagellin FliC), and the export gate platform protein FlhA. The substrates do not interact directly with FlhA; however, they are required to induce a binding-competent conformation to the chaperone that exposes the recognition motif featuring a highly conserved sequence recognized by FlhA. The structural data reveal the recognition signal in a class of T3SS proteins and provide new insight into the assembly of key protein complexes at the export gate. Bacterial flagella are composed of proteins secreted by a type III secretion system (T3SS), which requires the action of dedicated chaperones. Here, Xing et al. report the structures of two ternary complexes among flagellar chaperones, flagellar protein substrates, and the export gate platform protein.
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Affiliation(s)
- Qiong Xing
- Department of Structural Biology, St. Jude Children's Research Hospital, 263 Danny Thomas Place, Memphis, TN, 38105, USA
| | - Ke Shi
- Department of Biochemistry, Molecular Biology & Biophysics, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Athina Portaliou
- Laboratory of Molecular Bacteriology, Department of Microbiology & Immunology, Rega Institute for Medical Research, Katholicke Universiteit Leuven, 3000, Leuven, Belgium
| | - Paolo Rossi
- Department of Structural Biology, St. Jude Children's Research Hospital, 263 Danny Thomas Place, Memphis, TN, 38105, USA
| | - Anastassios Economou
- Laboratory of Molecular Bacteriology, Department of Microbiology & Immunology, Rega Institute for Medical Research, Katholicke Universiteit Leuven, 3000, Leuven, Belgium
| | - Charalampos G Kalodimos
- Department of Structural Biology, St. Jude Children's Research Hospital, 263 Danny Thomas Place, Memphis, TN, 38105, USA.
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42
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Terahara N, Inoue Y, Kodera N, Morimoto YV, Uchihashi T, Imada K, Ando T, Namba K, Minamino T. Insight into structural remodeling of the FlhA ring responsible for bacterial flagellar type III protein export. SCIENCE ADVANCES 2018; 4:eaao7054. [PMID: 29707633 PMCID: PMC5916509 DOI: 10.1126/sciadv.aao7054] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 03/09/2018] [Indexed: 06/08/2023]
Abstract
The bacterial flagellum is a supramolecular motility machine. Flagellar assembly begins with the basal body, followed by the hook and finally the filament. A carboxyl-terminal cytoplasmic domain of FlhA (FlhAC) forms a nonameric ring structure in the flagellar type III protein export apparatus and coordinates flagellar protein export with assembly. However, the mechanism of this process remains unknown. We report that a flexible linker of FlhAC (FlhAL) is required not only for FlhAC ring formation but also for substrate specificity switching of the protein export apparatus from the hook protein to the filament protein upon completion of the hook structure. FlhAL was required for cooperative ring formation of FlhAC. Alanine substitutions of residues involved in FlhAC ring formation interfered with the substrate specificity switching, thereby inhibiting filament assembly at the hook tip. These observations lead us to propose a mechanistic model for export switching involving structural remodeling of FlhAC.
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Affiliation(s)
- Naoya Terahara
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Yumi Inoue
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Noriyuki Kodera
- Bio-AFM Frontier Research Center, Kanazawa University, Kanazawa 920-1192, Japan
| | - Yusuke V. Morimoto
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
- RIKEN Quantitative Biology Center, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
- Department of Bioscience and Bioinformatics, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, 680-4 Kawazu, Iizuka, Fukuoka 820-8502, Japan
| | - Takayuki Uchihashi
- Bio-AFM Frontier Research Center, Kanazawa University, Kanazawa 920-1192, Japan
- Department of Physics, Kanazawa University, Kanazawa 920-1192, Japan
- Department of Physics, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Katsumi Imada
- Department of Macromolecular Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan
| | - Toshio Ando
- Bio-AFM Frontier Research Center, Kanazawa University, Kanazawa 920-1192, Japan
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Goban-cho, Chiyoda-ku, Tokyo 102-0076, Japan
| | - Keiichi Namba
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
- RIKEN Quantitative Biology Center, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
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43
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Inoue Y, Morimoto YV, Namba K, Minamino T. Novel insights into the mechanism of well-ordered assembly of bacterial flagellar proteins in Salmonella. Sci Rep 2018; 8:1787. [PMID: 29379125 PMCID: PMC5789064 DOI: 10.1038/s41598-018-20209-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Accepted: 01/15/2018] [Indexed: 11/24/2022] Open
Abstract
The FliI ATPase of the flagellar type III protein export apparatus forms the FliH2FliI complex along with its regulator FliH. The FliH2FliI complex is postulated to bring export substrates from the cytoplasm to the docking platform made of FlhA and FlhB although not essential for flagellar protein export. Here, to clarify the role of the FliH2FliI complex in flagellar assembly, we analysed the effect of FliH and FliI deletion on flagellar protein export and assembly. The hook length was not controlled properly in the ∆fliH-fliI flhB(P28T) mutant compared to wild-type cells, whose hook length is controlled to about 55 nm within 10% error. The FlhA(F459A) mutation increased the export level of the hook protein FlgE and the ruler protein FliK by about 10-fold and 3-fold, respectively, and improved the hook length control in the absence of FliH and FliI. However, the ∆fliH-fliI flhB(P28T) flhA(F459A) mutant did not produce flagellar filaments efficiently, and a large amount of flagellin monomers were leaked out into the culture media. Neither the hook length control nor flagellin leakage was affected by the FlhB(P28T) and FlhA(F459A) mutations. We will discuss a hierarchical protein export mechanism of the bacterial flagellum.
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Affiliation(s)
- Yumi Inoue
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Yusuke V Morimoto
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan.,Quantitative Biology Center, RIKEN, 6-2-3 Furuedai, Suita, Osaka, 565-0874, Japan.,Department of Bioscience and Bioinformatics, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, 680-4 Kawazu, Iizuka, Fukuoka, 820-8502, Japan
| | - Keiichi Namba
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan. .,Quantitative Biology Center, RIKEN, 6-2-3 Furuedai, Suita, Osaka, 565-0874, Japan.
| | - Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan.
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44
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Kinoshita M, Furukawa Y, Uchiyama S, Imada K, Namba K, Minamino T. Insight into adaptive remodeling of the rotor ring complex of the bacterial flagellar motor. Biochem Biophys Res Commun 2017; 496:12-17. [PMID: 29294326 DOI: 10.1016/j.bbrc.2017.12.118] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2017] [Revised: 12/04/2017] [Accepted: 12/20/2017] [Indexed: 12/23/2022]
Abstract
The bacterial flagellar motor rotates in both counterclockwise (CCW) and clockwise (CW) directions. FliG, FliM and FliN form the C ring on the cytoplasmic face of the MS ring made of a transmembrane protein, FliF. The C ring acts not only as a rotor but also as a switch of the direction of motor rotation. FliG consists of three domains: FliGN, FliGM and FliGC. FliGN directly binds to FliF. Intermolecular interactions between FliGM and FliGC drive FliG ring formation. FliGM is responsible for the interaction with FliM. FliGC is involved in the interaction with the stator protein MotA. Adaptive remodeling of the C ring occurs when the motor switches between the CCW and CW states. However, it remained unknown how. Here, we report the effects of a CW-locked deletion mutation (ΔPEV) in FliG of Thermotaoga maritia (Tm-FliG) on FliG-FliG and FliG-FliM interactions. The PEV deletion stabilized the intramolecular interaction between FliGM and FliGC, thereby suppressing the oligomerization of Tm-FliGMC in solution. This deletion also induced a conformational change of HelixMC connecting FliGM and FliGC to reduce the binding affinity of Tm-FliGMC for FliM. We will discuss adaptive remodeling of the C ring responsible for flagellar motor switching.
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Affiliation(s)
- Miki Kinoshita
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadoaka, Suita, Osaka 565-0871, Japan
| | - Yukio Furukawa
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadoaka, Suita, Osaka 565-0871, Japan
| | - Susumu Uchiyama
- Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Katsumi Imada
- Department of Macromolecular Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan
| | - Keiichi Namba
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadoaka, Suita, Osaka 565-0871, Japan; Quantitative Biology Center, RIKEN, 1-3 Yamadoaka, Suita, Osaka 565-0871, Japan
| | - Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadoaka, Suita, Osaka 565-0871, Japan.
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45
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Gaytán MO, Monjarás Feria J, Soto E, Espinosa N, Benítez JM, Georgellis D, González-Pedrajo B. Novel insights into the mechanism of SepL-mediated control of effector secretion in enteropathogenic Escherichia coli. Microbiologyopen 2017; 7:e00571. [PMID: 29277965 PMCID: PMC6011996 DOI: 10.1002/mbo3.571] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 10/30/2017] [Accepted: 11/03/2017] [Indexed: 11/13/2022] Open
Abstract
Type three secretion systems (T3SSs) are virulence determinants employed by several pathogenic bacteria as molecular syringes to inject effector proteins into host cells. Diarrhea‐producing enteropathogenic Escherichia coli (EPEC) uses a T3SS to colonize the intestinal tract. T3S is a highly coordinated process that ensures hierarchical delivery of three classes of substrates: early (inner rod and needle subunits), middle (translocators), and late (effectors). Translocation of effectors is triggered upon host‐cell contact in response to different environmental cues, such as calcium levels. The T3S substrate specificity switch from middle to late substrates in EPEC is regulated by the SepL and SepD proteins, which interact with each other and form a trimeric complex with the chaperone CesL. In this study, we investigated the link between calcium concentration and secretion regulation by the gatekeeper SepL. We found that calcium depletion promotes late substrate secretion in a translocon‐independent manner. Furthermore, the stability, formation, and subcellular localization of the SepL/SepD/CesL regulatory complex were not affected by the absence of calcium. In addition, we demonstrate that SepL interacts in a calcium‐independent manner with the major export gate component EscV, which in turn interacts with both middle and late secretion substrates, providing a docking site for T3S. These results suggest that EscV serves as a binding platform for both the SepL regulatory protein and secreted substrates during the ordered assembly of the T3SS.
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Affiliation(s)
- Meztlli O Gaytán
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
| | - Julia Monjarás Feria
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
| | - Eduardo Soto
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
| | - Norma Espinosa
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
| | - Julia M Benítez
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
| | - Dimitris Georgellis
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
| | - Bertha González-Pedrajo
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
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46
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Portaliou AG, Tsolis KC, Loos MS, Balabanidou V, Rayo J, Tsirigotaki A, Crepin VF, Frankel G, Kalodimos CG, Karamanou S, Economou A. Hierarchical protein targeting and secretion is controlled by an affinity switch in the type III secretion system of enteropathogenic Escherichia coli. EMBO J 2017; 36:3517-3531. [PMID: 29109154 DOI: 10.15252/embj.201797515] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 09/05/2017] [Accepted: 10/11/2017] [Indexed: 11/09/2022] Open
Abstract
Type III secretion (T3S), a protein export pathway common to Gram-negative pathogens, comprises a trans-envelope syringe, the injectisome, with a cytoplasm-facing translocase channel. Exported substrates are chaperone-delivered to the translocase, EscV in enteropathogenic Escherichia coli, and cross it in strict hierarchical manner, for example, first "translocators", then "effectors". We dissected T3S substrate targeting and hierarchical switching by reconstituting them in vitro using inverted inner membrane vesicles. EscV recruits and conformationally activates the tightly membrane-associated pseudo-effector SepL and its chaperone SepD. This renders SepL a high-affinity receptor for translocator/chaperone pairs, recognizing specific chaperone signals. In a second, SepD-coupled step, translocators docked on SepL become secreted. During translocator secretion, SepL/SepD suppress effector/chaperone binding to EscV and prevent premature effector secretion. Disengagement of the SepL/SepD switch directs EscV to dedicated effector export. These findings advance molecular understanding of T3S and reveal a novel mechanism for hierarchical trafficking regulation in protein secretion channels.
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Affiliation(s)
- Athina G Portaliou
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven, Leuven, Belgium
| | - Konstantinos C Tsolis
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven, Leuven, Belgium
| | - Maria S Loos
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven, Leuven, Belgium
| | - Vassileia Balabanidou
- Institute of Molecular Biology and Biotechnology, FORTH (Foundation of Research and Technology), University of Crete, Heraklion, Greece
| | - Josep Rayo
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven, Leuven, Belgium
| | - Alexandra Tsirigotaki
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven, Leuven, Belgium
| | - Valerie F Crepin
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK
| | - Gad Frankel
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK
| | | | - Spyridoula Karamanou
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven, Leuven, Belgium
| | - Anastassios Economou
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven, Leuven, Belgium
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47
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Fukumura T, Makino F, Dietsche T, Kinoshita M, Kato T, Wagner S, Namba K, Imada K, Minamino T. Assembly and stoichiometry of the core structure of the bacterial flagellar type III export gate complex. PLoS Biol 2017; 15:e2002281. [PMID: 28771466 PMCID: PMC5542437 DOI: 10.1371/journal.pbio.2002281] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 06/30/2017] [Indexed: 11/25/2022] Open
Abstract
The bacterial flagellar type III export apparatus, which is required for flagellar assembly beyond the cell membranes, consists of a transmembrane export gate complex and a cytoplasmic ATPase complex. FlhA, FlhB, FliP, FliQ, and FliR form the gate complex inside the basal body MS ring, although FliO is required for efficient export gate formation in Salmonella enterica. However, it remains unknown how they form the gate complex. Here we report that FliP forms a homohexameric ring with a diameter of 10 nm. Alanine substitutions of conserved Phe-137, Phe-150, and Glu-178 residues in the periplasmic domain of FliP (FliPP) inhibited FliP6 ring formation, suppressing flagellar protein export. FliO formed a 5-nm ring structure with 3 clamp-like structures that bind to the FliP6 ring. The crystal structure of FliPP derived from Thermotoga maritia, and structure-based photo-crosslinking experiments revealed that Phe-150 and Ser-156 of FliPP are involved in the FliP–FliP interactions and that Phe-150, Arg-152, Ser-156, and Pro-158 are responsible for the FliP–FliO interactions. Overexpression of FliP restored motility of a ∆fliO mutant to the wild-type level, suggesting that the FliP6 ring is a functional unit in the export gate complex and that FliO is not part of the final gate structure. Copurification assays revealed that FlhA, FlhB, FliQ, and FliR are associated with the FliO/FliP complex. We propose that the assembly of the export gate complex begins with FliP6 ring formation with the help of the FliO scaffold, followed by FliQ, FliR, and FlhB and finally FlhA during MS ring formation. The bacterial flagellar type III export gate complex is a membrane-embedded nanomachine responsible for flagellar protein export and exits in a patch of membrane within the central pore of the basal body MS ring. In this work, we investigate how formation of the export gate complex is initiated. The export gate complex is composed of 5 highly conserved transmembrane proteins: FlhA, FlhB, FliP, FliQ, and FliR. Each subunit protein assembles into the gate during MS ring formation in a well-coordinated manner. The transmembrane protein FliO is required for efficient assembly of the export gate complex in S. enterica but is not essential for flagellar protein export. Here we carry out biochemical and structural analyses of FliP and provide direct evidence suggesting that FliP forms a trimer-of-dimer structure with a diameter of 10 nm. The assembly of the export gate complex begins with FliP6 ring formation with the help of the FliO scaffold, followed by FliQ, FliR, and FlhB and finally FlhA during MS ring formation. Given the structural and functional similarities between the flagellar and the virulence-factor-delivering injectisome machineries, we propose that the periplasmic domain of FliP homologues of the injectisome could be a good target for novel antibiotics.
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Affiliation(s)
- Takuma Fukumura
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
| | - Fumiaki Makino
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
| | - Tobias Dietsche
- Interfactulty Institute of Microbiology and Infection Medicine, Section of Cellular and Molecular Microbiology, Eberhard Karls University Tübingen, Tübingen, Germany
| | - Miki Kinoshita
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
| | - Takayuki Kato
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
| | - Samuel Wagner
- Interfactulty Institute of Microbiology and Infection Medicine, Section of Cellular and Molecular Microbiology, Eberhard Karls University Tübingen, Tübingen, Germany
- German Center for Infection Research (DZIF), Partner-site Tübingen, Tübingen, Germany
| | - Keiichi Namba
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
- Quantitative Biology Center, Riken, Suita, Osaka, Japan
- * E-mail: (KN); (KI); (TM)
| | - Katsumi Imada
- Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan
- * E-mail: (KN); (KI); (TM)
| | - Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
- * E-mail: (KN); (KI); (TM)
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48
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Kinoshita M, Aizawa SI, Inoue Y, Namba K, Minamino T. The role of intrinsically disordered C-terminal region of FliK in substrate specificity switching of the bacterial flagellar type III export apparatus. Mol Microbiol 2017; 105:572-588. [PMID: 28557186 DOI: 10.1111/mmi.13718] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/24/2017] [Indexed: 01/06/2023]
Abstract
The bacterial flagellar export switching machinery consists of a ruler protein, FliK, and an export switch protein, FlhB and switches substrate specificity of the flagellar type III export apparatus upon completion of hook assembly. An interaction between the C-terminal domain of FliK (FliKC ) and the C-terminal cytoplasmic domain of FlhB (FlhBC ) is postulated to be responsible for this switch. FliKC has a compactly folded domain termed FliKT3S4 (residues 268-352) and an intrinsically disordered region composed of the last 53 residues, FliKCT (residues 353-405). Residues 301-350 of FliKT3S4 and the last five residues of FliKCT are critical for the switching function of FliK. FliKCT is postulated to regulate the interaction of FliKT3S4 with FlhBC , but it remains unknown how. Here we report the role of FliKCT in the export switching mechanism. Systematic deletion analyses of FliKCT revealed that residues of 351-370 are responsible for efficient switching of substrate specificity of the export apparatus. Suppressor mutant analyses showed that FliKCT coordinates FliKT3S4 action with the switching. Site-directed photo-cross-linking experiments showed that Val-302 and Ile-304 in the hydrophobic core of FliKT3S4 bind to FlhBC . We propose that FliKCT may induce conformational rearrangements of FliKT3S4 to bind to FlhBC .
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Affiliation(s)
- Miki Kinoshita
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Shin-Ichi Aizawa
- Department of Life Sciences, Prefectural University of Hiroshima, 562 Nanatsuka, Shobara, Hiroshima, 727-0023, Japan
| | - Yumi Inoue
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Keiichi Namba
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan.,Quantitative Biology Center, RIKEN, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
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49
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Radomska KA, Wösten MMSM, Ordoñez SR, Wagenaar JA, van Putten JPM. Importance of Campylobacter jejuni FliS and FliW in Flagella Biogenesis and Flagellin Secretion. Front Microbiol 2017; 8:1060. [PMID: 28659885 PMCID: PMC5466977 DOI: 10.3389/fmicb.2017.01060] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Accepted: 05/29/2017] [Indexed: 12/11/2022] Open
Abstract
Flagella-driven motility enables bacteria to reach their favorable niche within the host. The human foodborne pathogen Campylobacter jejuni produces two heavily glycosylated structural flagellins (FlaA and FlaB) that form the flagellar filament. It also encodes the non-structural FlaC flagellin which is secreted through the flagellum and has been implicated in host cell invasion. The mechanisms that regulate C. jejuni flagellin biogenesis and guide the proteins to the export apparatus are different from those in most other enteropathogens and are not fully understood. This work demonstrates the importance of the putative flagellar protein FliS in C. jejuni flagella assembly. A constructed fliS knockout strain was non-motile, displayed reduced levels of FlaA/B and FlaC flagellin, and carried severely truncated flagella. Pull-down and Far Western blot assays showed direct interaction of FliS with all three C. jejuni flagellins (FlaA, FlaB, and FlaC). This is in contrast to, the sensor and regulator of intracellular flagellin levels, FliW, which bound to FlaA and FlaB but not to FlaC. The FliS protein but not FliW preferred binding to glycosylated C. jejuni flagellins rather than to their non-glycosylated recombinant counterparts. Mapping of the binding region of FliS and FliW using a set of flagellin fragments showed that the C-terminal subdomain of the flagellin was required for FliS binding, whereas the N-terminal subdomain was essential for FliW binding. The separate binding subdomains required for FliS and FliW, the different substrate specificity, and the differential preference for binding of glycosylated flagellins ensure optimal processing and assembly of the C. jejuni flagellins.
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Affiliation(s)
- Katarzyna A Radomska
- Department of Infectious Diseases and Immunology, Utrecht UniversityUtrecht, Netherlands
| | - Marc M S M Wösten
- Department of Infectious Diseases and Immunology, Utrecht UniversityUtrecht, Netherlands
| | - Soledad R Ordoñez
- Department of Infectious Diseases and Immunology, Utrecht UniversityUtrecht, Netherlands
| | - Jaap A Wagenaar
- Department of Infectious Diseases and Immunology, Utrecht UniversityUtrecht, Netherlands.,Wageningen Bioveterinary ResearchLelystad, Netherlands.,WHO Collaborating Centre for Campylobacter/OIE Reference Laboratory for CampylobacteriosisUtrecht, Netherlands
| | - Jos P M van Putten
- Department of Infectious Diseases and Immunology, Utrecht UniversityUtrecht, Netherlands.,WHO Collaborating Centre for Campylobacter/OIE Reference Laboratory for CampylobacteriosisUtrecht, Netherlands
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50
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Gu H. Role of Flagella in the Pathogenesis of Helicobacter pylori. Curr Microbiol 2017; 74:863-869. [PMID: 28444418 PMCID: PMC5447363 DOI: 10.1007/s00284-017-1256-4] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 04/18/2017] [Indexed: 12/15/2022]
Abstract
This review aimed to investigate the role of Helicobacter pylori flagella on the pathogenicity of this bacterium in humans. Helicobacter pylori is a flagellated pathogen that colonizes the human gastroduodenal mucosa and produces inflammation, and is responsible for gastrointestinal disease. Its pathogenesis is attributed to colonization and virulence factors. The primary function of H. pylori flagella is to provide motility. We believe that H. pylori flagella play an important role in the colonization of the gastrointestinal mucosa. Therefore, we reviewed previous studies on flagellar morphology and motility in order to explore the relationship between H. pylori flagella and pathogenicity. Further investigation is required to confirm the association between flagella and pathogenicity in H. pylori.
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Affiliation(s)
- Haiying Gu
- Medical School, Ningbo University, Ningbo, 315211, China.
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