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Pandini A, Kleinjung J, Rasool S, Khan S. Coevolved Mutations Reveal Distinct Architectures for Two Core Proteins in the Bacterial Flagellar Motor. PLoS One 2015; 10:e0142407. [PMID: 26561852 PMCID: PMC4642947 DOI: 10.1371/journal.pone.0142407] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Accepted: 10/21/2015] [Indexed: 02/08/2023] Open
Abstract
Switching of bacterial flagellar rotation is caused by large domain movements of the FliG protein triggered by binding of the signal protein CheY to FliM. FliG and FliM form adjacent multi-subunit arrays within the basal body C-ring. The movements alter the interaction of the FliG C-terminal (FliGC) “torque” helix with the stator complexes. Atomic models based on the Salmonella entrovar C-ring electron microscopy reconstruction have implications for switching, but lack consensus on the relative locations of the FliG armadillo (ARM) domains (amino-terminal (FliGN), middle (FliGM) and FliGC) as well as changes during chemotaxis. The generality of the Salmonella model is challenged by the variation in motor morphology and response between species. We studied coevolved residue mutations to determine the unifying elements of switch architecture. Residue interactions, measured by their coevolution, were formalized as a network, guided by structural data. Our measurements reveal a common design with dedicated switch and motor modules. The FliM middle domain (FliMM) has extensive connectivity most simply explained by conserved intra and inter-subunit contacts. In contrast, FliG has patchy, complex architecture. Conserved structural motifs form interacting nodes in the coevolution network that wire FliMM to the FliGC C-terminal, four-helix motor module (C3-6). FliG C3-6 coevolution is organized around the torque helix, differently from other ARM domains. The nodes form separated, surface-proximal patches that are targeted by deleterious mutations as in other allosteric systems. The dominant node is formed by the EHPQ motif at the FliMMFliGM contact interface and adjacent helix residues at a central location within FliGM. The node interacts with nodes in the N-terminal FliGc α-helix triad (ARM-C) and FliGN. ARM-C, separated from C3-6 by the MFVF motif, has poor intra-network connectivity consistent with its variable orientation revealed by structural data. ARM-C could be the convertor element that provides mechanistic and species diversity.
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Affiliation(s)
- Alessandro Pandini
- Department of Computer Science and Synthetic Biology Theme, Brunel University London, Uxbridge UB8 3PH, United Kingdom
| | - Jens Kleinjung
- Mathematical Biology, Francis Crick Institute, Ridgeway, Mill Hill, London NW7 1AA, United Kingdom
| | - Shafqat Rasool
- Department of Biochemistry, McGill University, Montreal, QC H3G 1Y6, Canada
| | - Shahid Khan
- Molecular Biology Consortium, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States of America
- * E-mail:
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Lessons in Fundamental Mechanisms and Diverse Adaptations from the 2015 Bacterial Locomotion and Signal Transduction Meeting. J Bacteriol 2015. [PMID: 26195592 DOI: 10.1128/jb.00384-15] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In response to rapid changes in their environment, bacteria control a number of processes, including motility, cell division, biofilm formation, and virulence. Research presented in January 2015 at the biennial Bacterial Locomotion and Signal Transduction (BLAST) meeting in Tucson, AZ, illustrates the elegant complexity of the nanoarrays, nanomachines, and networks of interacting proteins that mediate such processes. Studies employing an array of biophysical, genetic, cell biology, and mathematical methods are providing an increasingly detailed understanding of the mechanisms of these systems within well-studied bacteria. Furthermore, comparisons of these processes in diverse bacterial species are providing insight into novel regulatory and functional mechanisms. This review summarizes research presented at the BLAST meeting on these fundamental mechanisms and diverse adaptations, including findings of importance for applications involving bacteria of medical or agricultural relevance.
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Onoue Y, Kojima S, Homma M. Effect of FliG three amino acids deletion in Vibrio polar-flagellar rotation and formation. J Biochem 2015; 158:523-9. [PMID: 26142283 DOI: 10.1093/jb/mvv068] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Accepted: 06/03/2015] [Indexed: 11/14/2022] Open
Abstract
Most of bacteria can swim by rotating flagella bidirectionally. The C ring, located at the bottom of the flagellum and in the cytoplasmic space, consists of FliG, FliM and FliN, and has an important function in flagellar protein secretion, torque generation and rotational switch of the motor. FliG is the most important part of the C ring that interacts directly with a stator subunit. Here, we introduced a three-amino acids in-frame deletion mutation (ΔPSA) into FliG from Vibrio alginolyticus, whose corresponding mutation in Salmonella confers a switch-locked phenotype, and examined its phenotype. We found that this FliG mutant could not produce flagellar filaments in a fliG null strain but the FliG(ΔPSA) protein could localize at the cell pole as does the wild-type protein. Unexpectedly, when this mutant was expressed in a wild-type strain, cells formed flagella efficiently but the motor could not rotate. We propose that this different phenotype in Vibrio and Salmonella might be due to distinct interactions between FliG mutant and FliM in the C ring between the bacterial species.
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Affiliation(s)
- Yasuhiro Onoue
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Seiji Kojima
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Michio Homma
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
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Abstract
The bacterial flagellum is driven by a bidirectional rotary motor, which propels bacteria to swim through liquids or swarm over surfaces. While the functions of the major structural and regulatory components of the flagellum are known, the function of the well-conserved FliL protein is not. In Salmonella and Escherichia coli, the absence of FliL leads to a small defect in swimming but complete elimination of swarming. Here, we tracked single motors of these bacteria and found that absence of FliL decreases their speed as well as switching frequency. We demonstrate that FliL interacts strongly with itself, with the MS ring protein FliF, and with the stator proteins MotA and MotB and weakly with the rotor switch protein FliG. These and other experiments show that FliL increases motor output either by recruiting or stabilizing the stators or by increasing their efficiency and contributes additionally to torque generation at higher motor loads. The increased torque enabled by FliL explains why this protein is essential for swarming on an agar surface expected to offer increased resistance to bacterial movement. FliL is a well-conserved bacterial flagellar protein whose absence leads to a variety of motility defects, ranging from moderate to complete inhibition of swimming in some bacterial species, inhibition of swarming in others, structural defects that break the flagellar rod during swarming in E. coli and Salmonella, and failure to eject the flagellar filament during the developmental transition of a swimmer to a stalk cell in Caulobacter crescentus. Despite these many phenotypes, a specific function for FliL has remained elusive. Here, we established a central role for FliL at the Salmonella and E. coli motors, where it interacts with both rotor and stator proteins, increases motor output, and contributes to the normal rotational bias of the motor.
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Nishino Y, Onoue Y, Kojima S, Homma M. Functional chimeras of flagellar stator proteins between E. coli MotB and Vibrio PomB at the periplasmic region in Vibrio or E. coli. Microbiologyopen 2015; 4:323-331. [PMID: 25630862 PMCID: PMC4398512 DOI: 10.1002/mbo3.240] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Revised: 12/24/2014] [Accepted: 01/10/2015] [Indexed: 12/27/2022] Open
Abstract
The bacterial flagellar motor has a stator and a rotor. The stator is composed of two membrane proteins, MotA and MotB in Escherichia coli and PomA and PomB in Vibrio alginolyticus. The Vibrio motor has a unique structure, the T ring, which is composed of MotX and MotY. Based on the structural information of PomB and MotB, we constructed three chimeric proteins between PomB and MotB, named PotB91 , PotB129, and PotB138 , with various chimeric junctions. When those chimeric proteins were produced with PomA in a ΔmotAB strain of E. coli or in ΔpomAB and ΔpomAB ΔmotX strains of Vibrio, all chimeras were functional in E. coli or Vibrio, either with or without the T ring, although the motilities were very weak in E. coli. Furthermore, we could isolate some suppressors in E. coli and identified the mutation sites on PomA or the chimeric B subunit. The weak function of chimeric PotBs in E. coli is derived mainly from the defect in the rotational switching of the flagellar motor. In addition, comparing the motilities of chimera strains in ΔpomAB, PotB138 had the highest motility. The difference between the origin of the α1 and α2 helices, E. coli MotB or Vibro PomB, seems to be important for motility in E. coli and especially in Vibrio.
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Affiliation(s)
- Yuuki Nishino
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, 464-8602, Japan
| | - Yasuhiro Onoue
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, 464-8602, Japan
| | - Seiji Kojima
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, 464-8602, Japan
| | - Michio Homma
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, 464-8602, Japan
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Minamino T, Imada K. The bacterial flagellar motor and its structural diversity. Trends Microbiol 2015; 23:267-74. [PMID: 25613993 DOI: 10.1016/j.tim.2014.12.011] [Citation(s) in RCA: 168] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 12/16/2014] [Accepted: 12/22/2014] [Indexed: 11/28/2022]
Abstract
The bacterial flagellum is a reversible rotary motor powered by an electrochemical-potential difference of specific ions across the cytoplasmic membrane. The H(+)-driven motor of Salmonella spins at ∼300 Hz, whereas the Na(+)-driven motor of marine Vibrio spp. can rotate much faster, up to 1700 Hz. A highly conserved motor structure consists of the MS ring, C ring, rod, and export apparatus. The C ring and the export apparatus show dynamic properties for exerting their functional activities. Various additional structures surrounding the conserved motor structure are observed in different bacterial species. In this review we summarize our current understanding of the structure, function, and assembly of the flagellar motor in Salmonella and marine Vibrio.
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Affiliation(s)
- Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, 1-3 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
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Sircar R, Borbat PP, Lynch MJ, Bhatnagar J, Beyersdorf MS, Halkides CJ, Freed JH, Crane BR. Assembly states of FliM and FliG within the flagellar switch complex. J Mol Biol 2014; 427:867-886. [PMID: 25536293 DOI: 10.1016/j.jmb.2014.12.009] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Revised: 12/12/2014] [Accepted: 12/12/2014] [Indexed: 01/11/2023]
Abstract
At the base of the bacterial flagella, a cytoplasmic rotor (the C-ring) generates torque and reverses rotation sense in response to stimuli. The bulk of the C-ring forms from many copies of the proteins FliG, FliM, and FliN, which together constitute the switch complex. To help resolve outstanding issues regarding C-ring architecture, we have investigated interactions between FliM and FliG from Thermotoga maritima with X-ray crystallography and pulsed dipolar ESR spectroscopy (PDS). A new crystal structure of an 11-unit FliG:FliM complex produces a large arc with a curvature consistent with the dimensions of the C-ring. Previously determined structures along with this new structure provided a basis to test switch complex assembly models. PDS combined with mutational studies and targeted cross-linking reveal that FliM and FliG interact through their middle domains to form both parallel and antiparallel arrangements in solution. Residue substitutions at predicted interfaces disrupt higher-order complexes that are primarily mediated by contacts between the C-terminal domain of FliG and the middle domain of a neighboring FliG molecule. Spin separations among multi-labeled components fit a self-consistent model that agree well with electron microscopy images of the C-ring. An activated form of the response regulator CheY destabilizes the parallel arrangement of FliM molecules to perturb FliG alignment in a process that may reflect the onset of rotation switching. These data suggest a model of C-ring assembly in which intermolecular contacts among FliG domains provide a template for FliM assembly and cooperative transitions.
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Affiliation(s)
- Ria Sircar
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - Peter P Borbat
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA; National Biomedical Center for Advanced ESR Technology, Cornell University, Ithaca, NY 14853, USA
| | - Michael J Lynch
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - Jaya Bhatnagar
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - Matthew S Beyersdorf
- Department of Chemistry and Biochemistry, Unversity of North Carolina Wilmington, Wilmington, NC 28403, USA
| | - Christopher J Halkides
- Department of Chemistry and Biochemistry, Unversity of North Carolina Wilmington, Wilmington, NC 28403, USA
| | - Jack H Freed
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA; National Biomedical Center for Advanced ESR Technology, Cornell University, Ithaca, NY 14853, USA
| | - Brian R Crane
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA.
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Interaction of the C-terminal tail of FliF with FliG from the Na+-driven flagellar motor of Vibrio alginolyticus. J Bacteriol 2014; 197:63-72. [PMID: 25313387 DOI: 10.1128/jb.02271-14] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rotation of the polar flagellum of Vibrio alginolyticus is driven by a Na(+)-type flagellar motor. FliG, one of the essential rotor proteins located at the upper rim of the C ring, binds to the membrane-embedded MS ring. The MS ring is composed of a single membrane protein, FliF, and serves as a foundation for flagellar assembly. Unexpectedly, about half of the Vibrio FliF protein produced at high levels in Escherichia coli was found in the soluble fraction. Soluble FliF purifies as an oligomer of ∼700 kDa, as judged by analytical size exclusion chromatography. By using fluorescence correlation spectroscopy, an interaction between a soluble FliF multimer and FliG was detected. This binding was weakened by a series of deletions at the C-terminal end of FliF and was nearly eliminated by a 24-residue deletion or a point mutation at a highly conserved tryptophan residue (W575). Mutations in FliF that caused a defect in FliF-FliG binding abolish flagellation and therefore confer a nonmotile phenotype. As data from in vitro binding assays using the soluble FliF multimer correlate with data from in vivo functional analyses, we conclude that the C-terminal region of the soluble form of FliF retains the ability to bind FliG. Our study confirms that the C-terminal tail of FliF provides the binding site for FliG and is thus required for flagellation in Vibrio, as reported for other species. This is the first report of detection of the FliF-FliG interaction in the Na(+)-driven flagellar motor, both in vivo and in vitro.
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Abstract
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The flagellum is one of the most
sophisticated self-assembling
molecular machines in bacteria. Powered by the proton-motive force,
the flagellum rapidly rotates in either a clockwise or counterclockwise
direction, which ultimately controls bacterial motility and behavior. Escherichia coli and Salmonella enterica have served as important model systems for extensive genetic, biochemical,
and structural analysis of the flagellum, providing unparalleled insights
into its structure, function, and gene regulation. Despite these advances,
our understanding of flagellar assembly and rotational mechanisms
remains incomplete, in part because of the limited structural information
available regarding the intact rotor–stator complex and secretion
apparatus. Cryo-electron tomography (cryo-ET) has become a valuable
imaging technique capable of visualizing the intact flagellar motor
in cells at molecular resolution. Because the resolution that can
be achieved by cryo-ET with large bacteria (such as E. coli and S. enterica) is limited, analysis of small-diameter
bacteria (including Borrelia burgdorferi and Campylobacter jejuni) can provide additional insights into
the in situ structure of the flagellar motor and
other cellular components. This review is focused on the application
of cryo-ET, in combination with genetic and biophysical approaches,
to the study of flagellar structures and its potential for improving
the understanding of rotor–stator interactions, the rotational
switching mechanism, and the secretion and assembly of flagellar components.
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Affiliation(s)
- Xiaowei Zhao
- Department of Pathology and Laboratory Medicine, University of Texas Medical School at Houston , Houston, Texas 77030, United States
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Takahashi Y, Ito M. Mutational analysis of charged residues in the cytoplasmic loops of MotA and MotP in the Bacillus subtilis flagellar motor. ACTA ACUST UNITED AC 2014; 156:211-20. [DOI: 10.1093/jb/mvu030] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Morimoto YV, Minamino T. Structure and function of the bi-directional bacterial flagellar motor. Biomolecules 2014; 4:217-34. [PMID: 24970213 PMCID: PMC4030992 DOI: 10.3390/biom4010217] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Revised: 01/24/2014] [Accepted: 02/04/2014] [Indexed: 01/02/2023] Open
Abstract
The bacterial flagellum is a locomotive organelle that propels the bacterial cell body in liquid environments. The flagellum is a supramolecular complex composed of about 30 different proteins and consists of at least three parts: a rotary motor, a universal joint, and a helical filament. The flagellar motor of Escherichia coli and Salmonella enterica is powered by an inward-directed electrochemical potential difference of protons across the cytoplasmic membrane. The flagellar motor consists of a rotor made of FliF, FliG, FliM and FliN and a dozen stators consisting of MotA and MotB. FliG, FliM and FliN also act as a molecular switch, enabling the motor to spin in both counterclockwise and clockwise directions. Each stator is anchored to the peptidoglycan layer through the C-terminal periplasmic domain of MotB and acts as a proton channel to couple the proton flow through the channel with torque generation. Highly conserved charged residues at the rotor–stator interface are required not only for torque generation but also for stator assembly around the rotor. In this review, we will summarize our current understanding of the structure and function of the proton-driven bacterial flagellar motor.
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Affiliation(s)
- Yusuke V Morimoto
- 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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Contribution of many charged residues at the stator-rotor interface of the Na+-driven flagellar motor to torque generation in Vibrio alginolyticus. J Bacteriol 2014; 196:1377-85. [PMID: 24464458 DOI: 10.1128/jb.01392-13] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
In torque generation by the bacterial flagellar motor, it has been suggested that electrostatic interactions between charged residues of MotA and FliG at the rotor-stator interface are important. However, the actual role(s) of those charged residues has not yet been clarified. In this study, we systematically made mutants of Vibrio alginolyticus whose charged residues of PomA (MotA homologue) and FliG were replaced by uncharged or charge-reversed residues and characterized the motilities of those mutants. We found that the members of a group of charged residues, 7 in PomA and 6 in FliG, collectively participate in torque generation of the Na(+)-driven flagellar motor in Vibrio. An additional specific interaction between PomA-E97 and FliG-K284 is critical for proper performance of the Vibrio motor. Our results also reveal that more charged residues are involved in the PomA-FliG interactions in the Vibrio Na(+)-driven motor than in the MotA-FliG interactions in the H(+)-driven one. This suggests that a larger number of conserved charged residues at the PomA-FliG interface contributes to the robustness of the Vibrio motor against mutations. The interaction surfaces of the stator and rotor of the Na(+)-driven motor seem to be more complex than those previously proposed in the H(+)-driven motor.
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63
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Gohara M, Kobayashi S, Abe-Yoshizumi R, Nonoyama N, Kojima S, Asami Y, Homma M. Biophysical characterization of the C-terminal region of FliG, an essential rotor component of the Na+-driven flagellar motor. J Biochem 2013; 155:83-9. [DOI: 10.1093/jb/mvt100] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
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Sircar R, Greenswag AR, Bilwes AM, Gonzalez-Bonet G, Crane BR. Structure and activity of the flagellar rotor protein FliY: a member of the CheC phosphatase family. J Biol Chem 2013; 288:13493-502. [PMID: 23532838 PMCID: PMC3650386 DOI: 10.1074/jbc.m112.445171] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND FliY is a flagellar rotor protein of the CheC phosphatase family. RESULTS The FliY structure resembles that of the rotor protein FliM but contains two active centers for CheY dephosphorylation. CONCLUSION FliY incorporates properties of the FliM/FliN rotor proteins and the CheC/CheX phosphatases to serve multiple functions in the flagellar switch. SIGNIFICANCE FliY distinguishes flagellar architecture and function in different types of bacteria. Rotating flagella propel bacteria toward favorable environments. Sense of rotation is determined by the intracellular response regulator CheY, which when phosphorylated (CheY-P) interacts directly with the flagellar motor. In many different types of bacteria, the CheC/CheX/FliY (CXY) family of phosphatases terminates the CheY-P signal. Unlike CheC and CheX, FliY is localized in the flagellar switch complex, which also contains the stator-coupling protein FliG and the target of CheY-P, FliM. The 2.5 Å resolution crystal structure of the FliY catalytic domain from Thermotoga maritima bears strong resemblance to the middle domain of FliM. Regions of FliM that mediate contacts within the rotor compose the phosphatase active sites in FliY. Despite the similarity between FliY and FliM, FliY does not bind FliG and thus is unlikely to be a substitute for FliM in the center of the switch complex. Solution studies indicate that FliY dimerizes through its C-terminal domains, which resemble the Escherichia coli switch complex component FliN. FliY differs topologically from the E. coli chemotaxis phosphatase CheZ but appears to utilize similar structural motifs for CheY dephosphorylation in close analogy to CheX. Recognition properties and phosphatase activities of site-directed mutants identify two pseudosymmetric active sites in FliY (Glu(35)/Asn(38) and Glu(132)/Asn(135)), with the second site (Glu(132)/Asn(135)) being more active. A putative N-terminal CheY binding domain conserved with FliM is not required for binding CheY-P or phosphatase activity.
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Affiliation(s)
- Ria Sircar
- From the Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14850
| | - Anna R. Greenswag
- From the Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14850
| | - Alexandrine M. Bilwes
- From the Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14850
| | - Gabriela Gonzalez-Bonet
- From the Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14850
| | - Brian R. Crane
- From the Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14850, To whom correspondence should be addressed: Dept. of Chemistry and Chemical Biology Cornell University, Ithaca, NY 14850. Tel.: 607-254-8634; E-mail:
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65
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Lam KH, Lam WWL, Wong JYK, Chan LC, Kotaka M, Ling TKW, Jin DY, Ottemann KM, Au SWN. Structural basis of FliG-FliM interaction inHelicobacter pylori. Mol Microbiol 2013; 88:798-812. [DOI: 10.1111/mmi.12222] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/31/2013] [Indexed: 12/20/2022]
Affiliation(s)
- Kwok-Ho Lam
- Center for Protein Science and Crystallography; School of Life Sciences; The Chinese University of Hong Kong; Hong Kong; China
| | - Wendy Wai Ling Lam
- Center for Protein Science and Crystallography; School of Life Sciences; The Chinese University of Hong Kong; Hong Kong; China
| | - Jase Yan-Kit Wong
- Center for Protein Science and Crystallography; School of Life Sciences; The Chinese University of Hong Kong; Hong Kong; China
| | - Ling-Chim Chan
- Department of Biochemistry; The University of Hong Kong; Hong Kong; China
| | - Masayo Kotaka
- Department of Physiology; The University of Hong Kong; Hong Kong; China
| | - Thomas Kin-Wah Ling
- Department of Microbiology; The Chinese University of Hong Kong; Hong Kong; China
| | - Dong-Yan Jin
- Department of Biochemistry; The University of Hong Kong; Hong Kong; China
| | - Karen M. Ottemann
- Department of Microbiology and Environmental Toxicology; University of California Santa Cruz; Santa Cruz; CA; USA
| | - Shannon Wing-Ngor Au
- Center for Protein Science and Crystallography; School of Life Sciences; The Chinese University of Hong Kong; Hong Kong; China
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66
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High hydrostatic pressure induces counterclockwise to clockwise reversals of the Escherichia coli flagellar motor. J Bacteriol 2013; 195:1809-14. [PMID: 23417485 DOI: 10.1128/jb.02139-12] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The bacterial flagellar motor is a reversible rotary machine that rotates a left-handed helical filament, allowing bacteria to swim toward a more favorable environment. The direction of rotation reverses from counterclockwise (CCW) to clockwise (CW), and vice versa, in response to input from the chemotaxis signaling circuit. CW rotation is normally caused by binding of the phosphorylated response regulator CheY (CheY-P), and strains lacking CheY are typically locked in CCW rotation. The detailed mechanism of switching remains unresolved because it is technically difficult to regulate the level of CheY-P within the concentration range that produces flagellar reversals. Here, we demonstrate that high hydrostatic pressure can induce CW rotation even in the absence of CheY-P. The rotation of single flagellar motors in Escherichia coli cells with the cheY gene deleted was monitored at various pressures and temperatures. Application of >120 MPa pressure induced a reversal from CCW to CW at 20°C, although at that temperature, no motor rotated CW at ambient pressure (0.1 MPa). At lower temperatures, pressure-induced changes in direction were observed at pressures of <120 MPa. CW rotation increased with pressure in a sigmoidal fashion, as it does in response to increasing concentrations of CheY-P. Application of pressure generally promotes the formation of clusters of ordered water molecules on the surfaces of proteins. It is possible that hydration of the switch complex at high pressure induces structural changes similar to those caused by the binding of CheY-P.
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Abe-Yoshizumi R, Kobayashi S, Gohara M, Hayashi K, Kojima C, Kojima S, Sudo Y, Asami Y, Homma M. Expression, purification and biochemical characterization of the cytoplasmic loop of PomA, a stator component of the Na(+) driven flagellar motor. Biophysics (Nagoya-shi) 2013; 9:21-9. [PMID: 27493537 PMCID: PMC4629686 DOI: 10.2142/biophysics.9.21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Accepted: 01/08/2013] [Indexed: 12/30/2022] Open
Abstract
Flagellar motors embedded in bacterial membranes are molecular machines powered by specific ion flows. Each motor is composed of a stator and a rotor and the interactions of those components are believed to generate the torque. Na+ influx through the PomA/PomB stator complex of Vibrio alginolyticus is coupled to torque generation and is speculated to trigger structural changes in the cytoplasmic domain of PomA that interacts with a rotor protein in the C-ring, FliG, to drive the rotation. In this study, we tried to overproduce the cytoplasmic loop of PomA (PomA-Loop), but it was insoluble. Thus, we made a fusion protein with a small soluble tag (GB1) which allowed us to express and characterize the recombinant protein. The structure of the PomA-Loop seems to be very elongated or has a loose tertiary structure. When the PomA-Loop protein was produced in E. coli, a slight dominant effect was observed on motility. We conclude that the cytoplasmic loop alone retains a certain function.
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Affiliation(s)
- Rei Abe-Yoshizumi
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Shiori Kobayashi
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Mizuki Gohara
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Kokoro Hayashi
- Laboratory of Biophysics, Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan
| | - Chojiro Kojima
- Laboratory of Biophysics, Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan
| | - Seiji Kojima
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Yuki Sudo
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Yasuo Asami
- TA Instruments Japan, Inc., 5-2-4, Nishi-gotanda, Shinagawa-ku, Tokyo 141-0031, Japan
| | - Michio Homma
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
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68
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Mechanism for adaptive remodeling of the bacterial flagellar switch. Proc Natl Acad Sci U S A 2012; 109:20018-22. [PMID: 23169659 DOI: 10.1073/pnas.1212327109] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The bacterial flagellar motor has been shown in previous work to adapt to changes in the steady-state concentration of the chemotaxis signaling molecule, CheY-P, by changing the FliM content. We show here that the number of FliM molecules in the motor and the fraction of FliM molecules that exchange depend on the direction of flagellar rotation, not on CheY-P binding per se. Our results are consistent with a model in which the structural differences associated with the direction of rotation modulate the strength of FliM binding. When the motor spins counterclockwise, FliM binding strengthens, the fraction of FliM molecules that exchanges decreases, and the ring content increases. The larger number of CheY-P binding sites enhances the motor's sensitivity, i.e., the motor adapts. An interesting unresolved question is how additional copies of FliM might be accommodated.
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69
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Distinct roles of highly conserved charged residues at the MotA-FliG interface in bacterial flagellar motor rotation. J Bacteriol 2012; 195:474-81. [PMID: 23161029 DOI: 10.1128/jb.01971-12] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Electrostatic interactions between the stator protein MotA and the rotor protein FliG are important for bacterial flagellar motor rotation. Arg90 and Glu98 of MotA are required not only for torque generation but also for stator assembly around the rotor, but their actual roles remain unknown. Here we analyzed the roles of functionally important charged residues at the MotA-FliG interface in motor performance. About 75% of the motA(R90E) cells and 45% of the motA(E98K) cells showed no fluorescent spots of green fluorescent protein (GFP)-MotB, indicating reduced efficiency of stator assembly around the rotor. The FliG(D289K) and FliG(R281V) mutations, which restore the motility of the motA(R90E) and motA(E98K) mutants, respectively, showed reduced numbers and intensity of GFP-MotB spots as well. The FliG(D289K) mutation significantly recovered the localization of GFP-MotB to the motor in the motA(R90E) mutant, whereas the FliG(R281V) mutation did not recover the GFP-MotB localization in the motA(E98K) mutant. These results suggest that the MotA-Arg90-FliG-Asp289 interaction is critical for the proper positioning of the stators around the rotor, whereas the MotA-Glu98-FliG-Arg281 interaction is more important for torque generation.
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70
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Vartanian AS, Paz A, Fortgang EA, Abramson J, Dahlquist FW. Structure of flagellar motor proteins in complex allows for insights into motor structure and switching. J Biol Chem 2012; 287:35779-83. [PMID: 22896702 PMCID: PMC3476246 DOI: 10.1074/jbc.c112.378380] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2012] [Revised: 06/12/2012] [Indexed: 12/23/2022] Open
Abstract
The flagellar motor is one type of propulsion device of motile bacteria. The cytoplasmic ring (C-ring) of the motor interacts with the stator to generate torque in clockwise and counterclockwise directions. The C-ring is composed of three proteins, FliM, FliN, and FliG. Together they form the "switch complex" and regulate switching and torque generation. Here we report the crystal structure of the middle domain of FliM in complex with the middle and C-terminal domains of FliG that shows the interaction surface and orientations of the proteins. In the complex, FliG assumes a compact conformation in which the middle and C-terminal domains (FliG(MC)) collapse and stack together similarly to the recently published structure of a mutant of FliG(MC) with a clockwise rotational bias. This intramolecular stacking of the domains is distinct from the intermolecular stacking seen in other structures of FliG. We fit the complex structure into the three-dimensional reconstructions of the motor and propose that the cytoplasmic ring is assembled from 34 FliG and FliM molecules in a 1:1 fashion.
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Affiliation(s)
- Armand S. Vartanian
- From the Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106 and
| | - Aviv Paz
- the Department of Physiology, David Geffen School of Medicine, UCLA, Los Angeles, California 90095
| | - Emily A. Fortgang
- From the Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106 and
| | - Jeff Abramson
- the Department of Physiology, David Geffen School of Medicine, UCLA, Los Angeles, California 90095
| | - Frederick W. Dahlquist
- From the Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106 and
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71
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Protein export according to schedule: architecture, assembly, and regulation of type III secretion systems from plant- and animal-pathogenic bacteria. Microbiol Mol Biol Rev 2012; 76:262-310. [PMID: 22688814 DOI: 10.1128/mmbr.05017-11] [Citation(s) in RCA: 304] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Flagellar and translocation-associated type III secretion (T3S) systems are present in most gram-negative plant- and animal-pathogenic bacteria and are often essential for bacterial motility or pathogenicity. The architectures of the complex membrane-spanning secretion apparatuses of both systems are similar, but they are associated with different extracellular appendages, including the flagellar hook and filament or the needle/pilus structures of translocation-associated T3S systems. The needle/pilus is connected to a bacterial translocon that is inserted into the host plasma membrane and mediates the transkingdom transport of bacterial effector proteins into eukaryotic cells. During the last 3 to 5 years, significant progress has been made in the characterization of membrane-associated core components and extracellular structures of T3S systems. Furthermore, transcriptional and posttranscriptional regulators that control T3S gene expression and substrate specificity have been described. Given the architecture of the T3S system, it is assumed that extracellular components of the secretion apparatus are secreted prior to effector proteins, suggesting that there is a hierarchy in T3S. The aim of this review is to summarize our current knowledge of T3S system components and associated control proteins from both plant- and animal-pathogenic bacteria.
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72
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Trp RNA-binding attenuation protein: modifying symmetry and stability of a circular oligomer. PLoS One 2012; 7:e44309. [PMID: 22970197 PMCID: PMC3435397 DOI: 10.1371/journal.pone.0044309] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Accepted: 08/01/2012] [Indexed: 11/19/2022] Open
Abstract
Background Subunit number is amongst the most important structural parameters that determine size, symmetry and geometry of a circular protein oligomer. The L-tryptophan biosynthesis regulator, TRAP, present in several Bacilli, is a good model system for investigating determinants of the oligomeric state. A short segment of C-terminal residues defines whether TRAP forms an 11-mer or 12-mer assembly. To understand which oligomeric state is more stable, we examine the stability of several wild type and mutant TRAP proteins. Methodology/Principal Findings Among the wild type B. stearothermophilus, B. halodurans and B. subtilis TRAP, we find that the former is the most stable whilst the latter is the least. Thermal stability of all TRAP is shown to increase with L-tryptophan concentration. We also find that mutant TRAP molecules that are truncated at the C-terminus - and hence induced to form 12-mers, distinct from their 11-mer wild type counterparts - have increased melting temperatures. We show that the same effect can be achieved by a point mutation S72N at a subunit interface, which leads to exclusion of C-terminal residues from the interface. Our findings are supported by dye-based scanning fluorimetry, CD spectroscopy, and by crystal structure and mass spectrometry analysis of the B. subtilis S72N TRAP. Conclusions/Significance We conclude that the oligomeric state of a circular protein can be changed by introducing a point mutation at a subunit interface. Exclusion (or deletion) of the C-terminus from the subunit interface has a major impact on properties of TRAP oligomers, making them more stable, and we argue that the cause of these changes is the altered oligomeric state. The more stable TRAP oligomers could be used in potential applications of TRAP in bionanotechnology.
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73
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Nanorotors and self-assembling macromolecular machines: The torque ring of the bacterial flagellar motor. Curr Opin Biotechnol 2012; 23:545-54. [DOI: 10.1016/j.copbio.2012.01.008] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2011] [Accepted: 01/16/2012] [Indexed: 01/18/2023]
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74
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Bacterial motility measured by a miniature chamber for high-pressure microscopy. Int J Mol Sci 2012; 13:9225-9239. [PMID: 22942763 PMCID: PMC3430294 DOI: 10.3390/ijms13079225] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Revised: 07/03/2012] [Accepted: 07/10/2012] [Indexed: 01/13/2023] Open
Abstract
Hydrostatic pressure is one of the physical stimuli that characterize the environment of living matter. Many microorganisms thrive under high pressure and may even physically or geochemically require this extreme environmental condition. In contrast, application of pressure is detrimental to most life on Earth; especially to living organisms under ambient pressure conditions. To study the mechanism of how living things adapt to high-pressure conditions, it is necessary to monitor directly the organism of interest under various pressure conditions. Here, we report a miniature chamber for high-pressure microscopy. The chamber was equipped with a built-in separator, in which water pressure was properly transduced to that of the sample solution. The apparatus developed could apply pressure up to 150 MPa, and enabled us to acquire bright-field and epifluorescence images at various pressures and temperatures. We demonstrated that the application of pressure acted directly and reversibly on the swimming motility of Escherichia coli cells. The present technique should be applicable to a wide range of dynamic biological processes that depend on applied pressures.
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75
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Multiple Conformations of the FliG C-Terminal Domain Provide Insight into Flagellar Motor Switching. Structure 2012; 20:315-25. [DOI: 10.1016/j.str.2011.11.020] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Revised: 11/25/2011] [Accepted: 11/29/2011] [Indexed: 01/01/2023]
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76
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Zarbiv G, Li H, Wolf A, Cecchini G, Caplan SR, Sourjik V, Eisenbach M. Energy complexes are apparently associated with the switch-motor complex of bacterial flagella. J Mol Biol 2011; 416:192-207. [PMID: 22210351 DOI: 10.1016/j.jmb.2011.12.027] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Revised: 12/12/2011] [Accepted: 12/13/2011] [Indexed: 01/27/2023]
Abstract
Recently, the switch-motor complex of bacterial flagella was found to be associated with a number of non-flagellar proteins, which, in spite of not being known as belonging to the chemotaxis system, affect the function of the flagella. The observation that one of these proteins, fumarate reductase, is essentially involved in electron transport under anaerobic conditions raised the question of whether other energy-linked enzymes are associated with the switch-motor complex as well. Here, we identified two additional such enzymes in Escherichia coli. Employing fluorescence resonance energy transfer in vivo and pull-down assays invitro, we provided evidence for the interaction of F(0)F(1) ATP synthase via its β subunit with the flagellar switch protein FliG and for the interaction of NADH-ubiquinone oxidoreductase with FliG, FliM, and possibly FliN. Furthermore, we measured higher rates of ATP synthesis, ATP hydrolysis, and electron transport from NADH to oxygen in membrane areas adjacent to the flagellar motor than in other membrane areas. All these observations suggest the association of energy complexes with the flagellar switch-motor complex. Finding that deletion of the β subunit in vivo affected the direction of flagellar rotation and switching frequency further implied that the interaction of F(0)F(1) ATP synthase with FliG is important for the function of the switch of bacterial flagella.
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Affiliation(s)
- Gabriel Zarbiv
- Department of Biological Chemistry, The Weizmann Institute of Science, 76100 Rehovot, Israel
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77
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A molecular mechanism of direction switching in the flagellar motor of Escherichia coli. Proc Natl Acad Sci U S A 2011; 108:17171-6. [PMID: 21969567 DOI: 10.1073/pnas.1110111108] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The direction of flagellar rotation is regulated by a rotor-mounted protein assembly, termed the "switch complex," formed from multiple copies of the proteins FliG, FliM, and FliN. The structures of major parts of these proteins are known, and the overall organization of proteins in the complex has been elucidated previously using a combination of protein-binding, mutational, and cross-linking approaches. In Escherichia coli, the switch from counterclockwise to clockwise rotation is triggered by the signaling protein phospho-CheY, which binds to the lower part of the switch complex and induces small movements of FliM and FliN subunits relative to each other. Direction switching also must produce movements in the upper part of the complex, particularly in the C-terminal domain of FliG (FliG(C)), which interacts with the stator to generate the torque for flagellar rotation. In the present study, protein movements in the middle and upper parts of the switch complex have been probed by means of targeted cross-linking and mutational analysis. Switching induces a tilting movement of the FliM domains that form the middle part of the switch and a consequent rotation of the affixed FliG(C) domains that reorients the stator interaction sites by about 90°. In a recently proposed hypothesis for the motor mechanism, such a reorientation of FliG(C) would reverse the direction of motor rotation.
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78
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Brown MT, Delalez NJ, Armitage JP. Protein dynamics and mechanisms controlling the rotational behaviour of the bacterial flagellar motor. Curr Opin Microbiol 2011; 14:734-40. [PMID: 21955888 DOI: 10.1016/j.mib.2011.09.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Revised: 09/01/2011] [Accepted: 09/08/2011] [Indexed: 10/17/2022]
Abstract
The proteins that make up the bacterial flagellar rotary motor have recently been shown to be more dynamic than previously thought, with some key proteins exchanging with pools of proteins in the membrane/cytoplasm. It has also become clear that in addition to simply switching in response to chemosensory signals, the rotation of the bacterial flagellar motor can be slowed or stopped, using a clutch or a brake, by signals from metabolism and growth state.
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Affiliation(s)
- Mostyn T Brown
- Oxford Centre for Integrative Systems Biology and Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
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79
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Koike M, Nishioka N, Kojima S, Homma M. Characterization of the flagellar motor composed of functional GFP-fusion derivatives of FliG in the Na +-driven polar flagellum of Vibrio alginolyticus. Biophysics (Nagoya-shi) 2011; 7:59-67. [PMID: 27857593 PMCID: PMC5036772 DOI: 10.2142/biophysics.7.59] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Accepted: 08/18/2011] [Indexed: 12/01/2022] Open
Abstract
The polar flagellum of Vibrio alginolyticus is driven by sodium ion flux via a stator complex, composed of PomA and PomB, across the cell membrane. The interaction between PomA and the rotor component FliG is believed to generate torque required for flagellar rotation. Previous research reported that a GFP-fused FliG retained function in the Vibrio flagellar motor. In this study, we found that N-terminal or C-terminal fusion of GFP has different effects on both torque generation and the switching frequency of the direction of flagellar motor rotation. We could detect the GFP-fused FliG in the basal-body (rotor) fraction although its association with the basal body was less stable than that of intact FliG. Furthermore, the fusion of GFP to the C-terminus of FliG, which is believed to be directly involved in torque generation, resulted in very slow motility and prohibited the directional change of motor rotation. On the other hand, the fusion of GFP to the N-terminus of FliG conferred almost the same swimming speed as intact FliG. These results are consistent with the premise that the C-terminal domain of FliG is directly involved in torque generation and the GFP fusions are useful to analyze the functions of various domains of FliG.
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Affiliation(s)
- Masafumi Koike
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-Ku, Nagoya 464-8602, Japan
| | - Noriko Nishioka
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-Ku, Nagoya 464-8602, Japan
| | - Seiji Kojima
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-Ku, Nagoya 464-8602, Japan
| | - Michio Homma
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-Ku, Nagoya 464-8602, Japan
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80
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Adjusting the spokes of the flagellar motor with the DNA-binding protein H-NS. J Bacteriol 2011; 193:5914-22. [PMID: 21890701 DOI: 10.1128/jb.05458-11] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The H-NS protein of bacteria is a global regulator that stimulates transcription of flagellar genes and that also acts directly to modulate flagellar motor function. H-NS is known to bind FliG, a protein of the rotor that interacts with the stator and is directly involved in rotation of the motor. Here, we find that H-NS, well known for its ability to organize DNA, acts in the flagellar motor to organize protein subunits in the rotor. It binds to a middle domain of FliG that bridges the core parts of the rotor and parts nearer the edge that interact with the stator. In the absence of H-NS the organization of FliG subunits is disrupted, whereas overexpression of H-NS enhances FliG organization as monitored by targeted disulfide cross-linking, alters the disposition of a helix joining the middle and C-terminal domains of FliG, and enhances motor performance under conditions requiring a strengthened rotor-stator interface. The H-NS homolog StpA was also shown to bind FliG and to act similarly, though less effectively, in organizing FliG. The motility-enhancing effects of H-NS contrast with those of the recently characterized motility inhibitor YcgR. The present findings provide an integrated, structurally grounded framework for understanding the roughly opposing effects of these motility regulators.
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81
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Paul K, Gonzalez-Bonet G, Bilwes AM, Crane BR, Blair D. Architecture of the flagellar rotor. EMBO J 2011; 30:2962-71. [PMID: 21673656 DOI: 10.1038/emboj.2011.188] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Accepted: 05/18/2011] [Indexed: 12/16/2022] Open
Abstract
Rotation and switching of the bacterial flagellum depends on a large rotor-mounted protein assembly composed of the proteins FliG, FliM and FliN, with FliG most directly involved in rotation. The crystal structure of a complex between the central domains of FliG and FliM, in conjunction with several biochemical and molecular-genetic experiments, reveals the arrangement of the FliG and FliM proteins in the rotor. A stoichiometric mismatch between FliG (26 subunits) and FliM (34 subunits) is explained in terms of two distinct positions for FliM: one where it binds the FliG central domain and another where it binds the FliG C-terminal domain. This architecture provides a structural framework for addressing the mechanisms of motor rotation and direction switching and for unifying the large body of data on motor performance. Recently proposed alternative models of rotor assembly, based on a subunit contact observed in crystals, are not supported by experiment.
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Affiliation(s)
- Koushik Paul
- Department of Biology, University of Utah, Salt Lake City, UT, USA
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