Structure of the torque ring of the flagellar motor and the molecular basis for rotational switching

Lee, Lawrence K.; Ginsburg, Michael A.; Crovace, Claudia; Donohoe, Mhairi; Stock, Daniela

doi:10.1038/nature09300

Cited by 163 publications

(281 citation statements)

References 39 publications

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“…High-resolution cryoelectron-microscopy reconstructions of BFM rotors in Salmonella show an inner ring with 24-to 26-fold symmetry and an outer ring with 32-to 36-fold symmetry (45). A recent structural model based on atomic-resolution crystal structures of the rotor protein that is thought to be the "track" on which stators exert torque, FliG from Aquifex aeolicus, predicts a 34-fold symmetric ring of FliG molecules (46). Thus, our estimate of N is compatible with the latest structural evidence, given the experimental uncertainty and the possibility of slight variations in N between bacterial species.…”

Section: Discussionmentioning

confidence: 99%

Mechanism and kinetics of a sodium-driven bacterial flagellar motor

Sowa

Pilizota

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

104

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The bacterial flagellar motor is a large rotary molecular machine that propels swimming bacteria, powered by a transmembrane electrochemical potential difference. It consists of an ∼50-nm rotor and up to ∼10 independent stators anchored to the cell wall. We measured torque-speed relationships of single-stator motors under 25 different combinations of electrical and chemical potential. All 25 torque-speed curves had the same concave-down shape as fully energized wild-type motors, and each stator passes at least 37 ± 2 ions per revolution. We used the results to explore the 25-dimensional parameter space of generalized kinetic models for the motor mechanism, finding 830 parameter sets consistent with the data. Analysis of these sets showed that the motor mechanism has a "powerstroke" in either ion binding or transit; ion transit is channel-like rather than carrier-like; and the rate-limiting step in the motor cycle is ion binding at low concentration, ion transit, or release at high concentration. where V m is the membrane voltage and Δμ = k B T ln(C in /C out ) and q are the transmembrane chemical potential difference and charge of the ions, respectively, with C in and C out the internal and external ion concentrations. In most species the primary form of biological free energy is the proton-motive force (PMF), the IMF for H + ions (1). Physiological PMF is typically in the range −150 mV to −200 mV, with the inside electrically negative and slightly alkaline relative to the outside. Some organisms use sodium-motive force (SMF) to drive numerous cellular processes, such as bacterial motility (2), ATP synthesis (3), and active membrane transport (4). Arguably the most important process driven by IMF is ATP synthesis, which generates cellular ATP by forced rotation of the F 1 part of F 1 F O ATP-synthase. F 1 is mechanically coupled to and rotated by F O , which like the bacterial flagellar motor (BFM) is an ion-driven rotary motor. Understanding the mechanism of these and other ion-driven molecular machines is a fundamental challenge in cellular energetics and biophysics. The BFM (Fig. 1A) is a rotary molecular machine that propels many species of swimming bacteria. It couples ion flow, for example protons (H + ) in Escherichia coli or sodium ions (Na + ) in Vibrio alginolyticus, to the rotation of extracellular helical flagellar filaments at hundreds of revolutions per second (Hz) (2, 5, 6). Torque is generated by interactions between stator complexes (containing the proteins MotA and MotB in E. coli and PomA and PomB in V. alginolyticus) and the rotor protein FliG (7). In E. coli, each motor can be powered by any number between 1 and at least 11 functionally independent stators (8), which exchange with a membrane-bound pool of "spare" stators on a timescale of minutes (9).The most important biophysical method for studying the torque-generating mechanism of the BFM has been to measure its torque-speed curves. This has been done using varying viscous load (10-14) or external torque (15, 16) to control the speed. Fu...

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Section: Discussionmentioning

confidence: 99%

Mechanism and kinetics of a sodium-driven bacterial flagellar motor

Sowa

Pilizota

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

104

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“…MotA interacts with the cytoplasmic FliG protein, which forms a ring of 26-fold symmetry on the cytoplasmic side of the MS ring and is directly involved in torque generation (183,309,325,326,535,637). FliG is part of the switch complex that is required for flagellar rotation and the switching between clockwise and counterclockwise rotation.…”

Section: Power Supplies-the Cytoplasmic Atpase and The Flagellar Motormentioning

confidence: 99%

Protein Export According to Schedule: Architecture, Assembly, and Regulation of Type III Secretion Systems from Plant- and Animal-Pathogenic Bacteria

Büttner

2012

Microbiol Mol Biol Rev

366

482

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SUMMARY 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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“…FliG Cdomain is proximal to the membrane. Finally, FliG middle domain is arranged to form an ARM super helix (Lee et al, 2010). Even though the model seems to give a better accord with EM data, no explanation is given about the symmetry mismatching.…”

Section: Model Amentioning

confidence: 75%

“…It allows the bacterium to reorient its swimming, from Counterclockwise (CCW) to Clockwise (CW) (Lee et al, 2010). The motion is controlled through a chemotactic signal, consisting in proteins CheW/CheA and CheY.…”

Section: H Pylori Switch Proteinsmentioning

confidence: 99%

Structural Characterization at the Atomic Level of a Molecular Nano-Machine: The State of the Art of <i>Helicobacter Pylori</i> Flagellum Organization

Pulić¹,

Loconte²,

Zanotti³

2014

American Journal of Biochemistry and Biotechnology

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Motility is fundamental for success in colonization and survival of the human pathogen H. pylori, the bacterium that colonizes about half of the human population. Motility is achieved through flagella. In this review the present structural knowledge about the organization of H. pylori flagella is summarized, considering not only the structure of its proteins, but also what is known about flagella of other Gram-negative bacteria. Despite the limited amount of structural information about the H. pylori nano-machinery, sequence alignments and homology modeling allow to investigate the unique structural properties of several H. pylori flagellar proteins.

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Structure of the torque ring of the flagellar motor and the molecular basis for rotational switching

Cited by 163 publications

References 39 publications

Mechanism and kinetics of a sodium-driven bacterial flagellar motor

Mechanism and kinetics of a sodium-driven bacterial flagellar motor

Protein Export According to Schedule: Architecture, Assembly, and Regulation of Type III Secretion Systems from Plant- and Animal-Pathogenic Bacteria

Structural Characterization at the Atomic Level of a Molecular Nano-Machine: The State of the Art of <i>Helicobacter Pylori</i> Flagellum Organization

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