Directional Switching Mechanism of the Bacterial Flagellar Motor

Minamino, Tetsuo; Kinoshita, Miki; Namba, Keiichi

doi:10.1016/j.csbj.2019.07.020

Cited by 53 publications

(50 citation statements)

References 75 publications

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“…Any mechanism for coupling ion flow to flagellar rotation must also explain how the direction of rotation of the flagellum can reverse in response to chemotactic stimuli. All experimental evidence (reviewed in 28 ) shows that the chemotaxis machinery acts on the FliG subunit of the C-ring rather than the stator. Our unidirectional rotation model for the stator mechanism can account for flagellar reversal if the chemotaxis-linked conformational changes induced in the C-ring lead to an alteration in the side of the stator that is driving the rotation (Fig.…”

Section: Mainmentioning

confidence: 99%

Structures of the stator complex that drives rotation of the bacterial flagellum

Deme

Johnson

Vickery

et al. 2020

Preprint

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The bacterial flagellum is the proto-typical protein nanomachine and comprises a 22 rotating helical propeller attached to a membrane-embedded motor complex 1 . The motor 23 consists of a central rotor surround by stator units that couple ion flow across the cytoplasmic 24 membrane to torque generation. Here we present the structures of stator complexes from 25 multiple bacterial species, allowing interpretation of the extensive body of data on stator 26 mechanism. The structures reveal an unexpected asymmetric A5B2 subunit assembly in which 27 the five A subunits enclose the two B subunits. Comparison to novel structures of other ion-28 driven motors indicates that this A5B2 architecture is fundamental to bacterial systems that 29 2 couple energy from ion-flow to generate mechanical work at a distance, and suggests that 30 such events involve rotation in the motor structures. 31 32Main 33A motor is a machine that supplies motive power for a device with moving parts. 34Biological systems use both linear and rotary motors to generate a variety of outputs. One of 35 the most fascinating and complex biological rotary motors is the flagellar apparatus used by 36 bacteria to propel themselves through fluid environments. Although bacterial swimming was 37 first observed in the 17 th century 2 , a mechanistic understanding of how the bacterial flagellum 38 generates rotation is still lacking. The core of the flagellum is a highly conserved motor (Fig. 39 1a) consisting of a cytoplasmic-membrane embedded rotor complex surrounded by varying 40 numbers of stator complexes (hereafter termed simply stators) that generate torque 3 . While 41 high resolution information has recently been obtained for the rotor component 4 , structural 42 detail of the stators has thus far been limited to modelling studies 5 . 43Stators harvest energy from either H + or Na + ion flow across the cytoplasmic 44 membrane, generating torque in the cytoplasmic portion (C-ring) of the rotor complex 6-9 . 45

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Section: Mainmentioning

confidence: 99%

Structures of the stator complex that drives rotation of the bacterial flagellum

Deme

Johnson

Vickery

et al. 2020

Preprint

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“…A sophisticated chemotaxis signaling system allows the cell to sense chemical stimuli and transmit this information via a phosphorylated form of the response regulator CheY to regulate the direction of rotation 5,6 . Although it is well known that lower levels of CheY-P promote CCW rotation and higher levels promote CW rotation, the exact mechanism of CheY-P induced rotational switching is unknown 1,3,4 . Intriguingly, recent data suggest that flagellar switch proteins are highly dynamic and that the number of subunits vary significantly in E. coli and S. enterica motors rotating CCW and CW 7,8 .…”

Section: Introductionmentioning

confidence: 99%

“…FliG1 is located at one cell pole; it remains unknown if it is a part of the C-ring 23 . FliM and FliN are extensively involved in switching the direction of the motor 3 .…”

Section: Introductionmentioning

confidence: 99%

Molecular Mechanism for Rotational Switching of the Bacterial Flagellar Motor

Chang

Zhang

Carroll

et al. 2020

Preprint

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23The bacterial flagellar motor is a remarkable nanomachine that can rapidly rotate in both 24 counter-clockwise (CCW) and clockwise (CW) senses. The transitions between CCW and CW 25 rotation are critical for chemotaxis, and they are controlled by a signaling protein (CheY-P) 26 that interacts with a switch complex at the cytoplasmic side of the flagellar motor. However, 27 the exact molecular mechanism by which CheY-P controls the motor rotational switch remains 28 enigmatic. Here, we use the Lyme disease spirochete, Borrelia burgdorferi, as the model 29 system to dissect the mechanism underlying flagellar rotational switching. We first determined 30 high resolution in situ motor structures in the cheX and cheY3 mutants in which motors are 31 genetically locked in CCW or CW rotation. The structures showed that the CheY3 protein of 32 B. burgdorferi interacts directly with the FliM protein of the switch complex in a 33 phosphorylation-dependent manner. The binding of CheY3-P to FliM induces a major 34 remodeling of the switch protein FliG2 that alters its interaction with the torque generator. 35Because the remodeling of FliG2 is directly correlated with the rotational direction, our data 36 lead to a model for flagellar function in which the torque generator rotates in response to an 37 inward flow of H + driven by the proton motive force. Rapid conformational changes of FliG2 38 allow the switch complex to interact with opposite sides of the rotating torque generator, 39 thereby facilitating rotational switching between CW and CCW. 40 assembling the collar, stator complexes, and C-ring together, we revealed a complex 130 architecture of the CW-rotating flagellar motor with unprecedented details (Fig. 1h, i). 131 132 CheY3-P binds to the FliM protein of the C-ring 133The well-defined C-ring in the ∆cheX mutant was found to be associated with two previously 134 unidentified densities (arrowheads indicated in Fig. 1d, e). We hypothesized that these 135 densities represent bound CheY3-P, as high levels of CheY3-P are expected in the ∆cheX 136 cells 14 . To characterize CheY3-P and its interaction with the ∆cheX motor, we replaced the 137 cheX-cheY3 genes with cheY3-gfp, generating a cheX::cheY3-GFP mutant (Extended Data Fig. 138

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“…The ion-powered rotary motor consists of a rotor surrounded by a ring of stator protein complexes (MotAB) that power its rotation (9)(10)(11)(12). The motor is bidirectional: chemotactic signaling can cause a conformational change in the rotor, known as "switching" (13), which results in a change of the rotational direction of the motor. 30…”

mentioning

confidence: 99%

“…The stator unit protein MotA is thought to contact the FliG protein (through the torque helix (HelixTorque) of the C-terminal domain FliGCC) which forms part of the cytoplasmic C-ring of the rotor. In this way, the proposed conformational changes in the stator unit are driving rotation of the rotor (13,(22)(23)(24). A large body of genetic data 45 is available on mutations in the motor that affect movement and are characterized as Mot -(non-3 motile, i.e.…”

mentioning

confidence: 99%

Structure and function of stator units of the bacterial flagellar motor

Santiveri

Roa-Eguiara

Kühne

et al. 2020

Preprint

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Many bacteria use the flagellum for locomotion and chemotaxis. Its bi-directional rotation is driven by the membrane-embedded motor, which uses energy from the transmembrane ion gradient to generate torque at the interface between stator units and rotor. The structural organization of the stator unit (MotAB), its conformational changes upon ion transport and how 15 these changes power rotation of the flagellum, remain unknown. Here we present ~3 Å-resolution cryo-electron microscopy reconstructions of the stator unit in different functional states. We show that the stator unit consists of a dimer of MotB surrounded by a pentamer of MotA. Combining structural data with mutagenesis and functional studies, we identify key residues involved in torque generation and present a mechanistic model for motor function and switching of rotational 20 direction.One Sentence Summary: Structural basis of torque generation in the bidirectional bacterial flagellar motor

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Directional Switching Mechanism of the Bacterial Flagellar Motor

Cited by 53 publications

References 75 publications

Structures of the stator complex that drives rotation of the bacterial flagellum

Structures of the stator complex that drives rotation of the bacterial flagellum

Molecular Mechanism for Rotational Switching of the Bacterial Flagellar Motor

Structure and function of stator units of the bacterial flagellar motor

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