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Molecular mechanism for rotational switching of the bacterial flagellar motor

Nature Structural & Molecular Biology volume 27, pages 1041–1047 (2020)Cite this article

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Abstract

The bacterial flagellar motor can rotate in counterclockwise (CCW) or clockwise (CW) senses, and transitions are controlled by the phosphorylated form of the response regulator CheY (CheY-P). To dissect the mechanism underlying flagellar rotational switching, we use Borrelia burgdorferi as a model system to determine high-resolution in situ motor structures in cheX and cheY3 mutants, in which motors are locked in either CCW or CW rotation. The structures showed that CheY3-P interacts directly with a switch protein, FliM, inducing a major remodeling of another switch protein, FliG2, and altering its interaction with the torque generator. Our findings lead to a model in which the torque generator rotates in response to an inward flow of H+ driven by the proton motive force, and conformational changes in FliG2 driven by CheY3-P allow the switch complex to interact with opposite sides of the rotating torque generator, facilitating rotational switching.

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Fig. 1: Structure of the flagellar motor in constantly flexing ∆cheX cells.
Fig. 2: CheY3-P binding to the flagellar motor.
Fig. 3: Stator–rotor interactions in constantly running ∆cheY3 cells.
Fig. 4: Molecular architectures of the flagellar motors without and with CheY3-P.
Fig. 5: Model for the mechanism of rotational switching.

Data availability

Cryo-EM density maps that support the local refined ∆cheX (EMD-21885) and ∆cheY3 (class-1: EMD-21884, class-2: EMD-21886) motor structures determined by cryo-electron tomography have been deposited in the Electron Microscopy Data Bank (EMDB). Other maps and models are available upon request.

References

  1. Berg, H. C. The rotary motor of bacterial flagella. Annu. Rev. Biochem. 72, 19–54 (2003).

    Article  CAS  PubMed  Google Scholar 

  2. Chevance, F. F. & Hughes, K. T. Coordinating assembly of a bacterial macromolecular machine. Nat. Rev. Microbiol. 6, 455–465 (2008).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  3. Minamino, T., Kinoshita, M. & Namba, K. Directional switching mechanism of the bacterial flagellar motor. Comput. Struct. Biotechnol. J. 17, 1075–1081 (2019).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  4. Terashima, H., Kojima, S. & Homma, M. Flagellar motility in bacteria structure and function of flagellar motor. Int. Rev. Cell Mol. Biol. 270, 39–85 (2008).

    Article  CAS  PubMed  Google Scholar 

  5. Wadhams, G. H. & Armitage, J. P. Making sense of it all: bacterial chemotaxis. Nat. Rev. Mol. Cell Biol. 5, 1024–1037 (2004).

    Article  CAS  PubMed  Google Scholar 

  6. Parkinson, J. S., Hazelbauer, G. L. & Falke, J. J. Signaling and sensory adaptation in Escherichia coli chemoreceptors: 2015 update. Trends Microbiol. 23, 257–266 (2015).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  7. Rossmann, F. M., Hug, I., Sangermani, M., Jenal, U. & Beeby, M. In situ structure of the Caulobacter crescentus flagellar motor and visualization of binding of a CheY-homolog. Mol. Microbiol. https://doi.org/10.1111/mmi.14525 (2020).

  8. Lele, P. P., Branch, R. W., Nathan, V. S. & Berg, H. C. Mechanism for adaptive remodeling of the bacterial flagellar switch. Proc. Natl Acad. Sci. USA 109, 20018–20022 (2012).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  9. Delalez, N. J., Berry, R. M. & Armitage, J. P. Stoichiometry and turnover of the bacterial flagellar switch protein FliN. Mbio 5, e01216-14 (2014).

    Article  PubMed  PubMed Central  CAS  Google Scholar 

  10. Charon, N. W. et al. The unique paradigm of spirochete motility and chemotaxis. Annu. Rev. Microbiol 66, 349–370 (2012).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  11. Nakamura, S. Spirochete flagella and motility. Biomolecules 10, 550 (2020).

    Article  CAS  PubMed Central  Google Scholar 

  12. Berg, H. C. How spirochetes may swim. J. Theor. Biol. 56, 269–273 (1976).

    Article  CAS  PubMed  Google Scholar 

  13. Li, C. et al. Asymmetrical flagellar rotation in Borrelia burgdorferi nonchemotactic mutants. Proc. Natl Acad. Sci. USA 99, 6169–6174 (2002).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  14. Motaleb, M. A., Liu, J. & Wooten, R. M. Spirochetal motility and chemotaxis in the natural enzootic cycle and development of Lyme disease. Curr. Opin. Microbiol. 28, 106–113 (2015).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  15. Motaleb, M. A. et al. CheX is a phosphorylated CheY phosphatase essential for Borrelia burgdorferi chemotaxis. J. Bacteriol. 187, 7963–7969 (2005).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  16. Chen, S. et al. Structural diversity of bacterial flagellar motors. EMBO J. 30, 2972–2981 (2011).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  17. Zhao, X., Norris, S. J. & Liu, J. Molecular architecture of the bacterial flagellar motor in cells. Biochemistry 53, 4323–4333 (2014).

    Article  CAS  PubMed  Google Scholar 

  18. Kojima, S. & Blair, D. F. The bacterial flagellar motor: structure and function of a complex molecular machine. Int. Rev. Cytol. 233, 93–134 (2004).

    Article  CAS  PubMed  Google Scholar 

  19. Chang, Y. et al. Structural insights into flagellar stator-rotor interactions. Elife 8, e48979 (2019).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  20. Zhou, J., Lloyd, S. A. & Blair, D. F. Electrostatic interactions between rotor and stator in the bacterial flagellar motor. Proc. Natl Acad. Sci. USA 95, 6436–6441 (1998).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  21. Chun, S. Y. & Parkinson, J. S. Bacterial motility: membrane topology of the Escherichia coli MotB protein. Science 239, 276–278 (1988).

    Article  CAS  PubMed  Google Scholar 

  22. Kojima, S. et al. The helix rearrangement in the periplasmic domain of the flagellar stator B subunit activates peptidoglycan binding and ion influx. Structure 26, 590–598.e5 (2018).

    Article  CAS  PubMed  Google Scholar 

  23. Lloyd, S. A. & Blair, D. F. Charged residues of the rotor protein FliG essential for torque generation in the flagellar motor of Escherichia coli. J. Mol. Biol. 266, 733–744 (1997).

    Article  CAS  PubMed  Google Scholar 

  24. Li, C., Xu, H., Zhang, K. & Liang, F. T. Inactivation of a putative flagellar motor switch protein FliG1 prevents Borrelia burgdorferi from swimming in highly viscous media and blocks its infectivity. Mol. Microbiol. 75, 1563–1576 (2010).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  25. Deme, J. C. et al. Structures of the stator complex that drives rotation of the bacterial flagellum. Preprint at bioRxiv https://doi.org/10.1101/2020.05.12.089201 (2020).

  26. Santiveri, M. et al. Structure and function of stator units of the bacterial flagellar motor. Preprint at bioRxiv https://doi.org/10.1101/2020.05.15.096610 (2020).

  27. Takekawa, N. et al. The tetrameric MotA complex as the core of the flagellar motor stator from hyperthermophilic bacterium. Sci. Rep. 6, 31526 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  28. Kojima, S. et al. Stator assembly and activation mechanism of the flagellar motor by the periplasmic region of MotB. Mol. Microbiol. 73, 710–718 (2009).

    Article  CAS  PubMed  Google Scholar 

  29. Thomas, D. R., Francis, N. R., Xu, C. & DeRosier, D. J. The three-dimensional structure of the flagellar rotor from a clockwise-locked mutant of Salmonella enterica serovar Typhimurium. J. Bacteriol. 188, 7039–7048 (2006).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  30. Motaleb, M. A., Sultan, S. Z., Miller, M. R., Li, C. & Charon, N. W. CheY3 of Borrelia burgdorferi is the key response regulator essential for chemotaxis and forms a long-lived phosphorylated intermediate. J. Bacteriol. 193, 3332–3341 (2011).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  31. McDowell, M. A. et al. Characterisation of Shigella Spa33 and Thermotoga FliM/N reveals a new model for C-ring assembly in T3SS. Mol. Microbiol. 99, 749–766 (2016).

    Article  CAS  PubMed  Google Scholar 

  32. Carroll, B. L. et al. The flagellar motor of Vibrio alginolyticus undergoes major structural remodeling during rotational switching. Preprint at bioRxiv https://doi.org/10.1101/2020.04.24.060053 (2020).

  33. Leake, M. C. et al. Stoichiometry and turnover in single, functioning membrane protein complexes. Nature 443, 355–358 (2006).

    Article  CAS  PubMed  Google Scholar 

  34. Vartanian, A. S., Paz, A., Fortgang, E. A., Abramson, J. & Dahlquist, F. W. Structure of flagellar motor proteins in complex allows for insights into motor structure and switching. J. Biol. Chem. 287, 35779–35783 (2012).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  35. Lee, L. K., Ginsburg, M. A., Crovace, C., Donohoe, M. & Stock, D. Structure of the torque ring of the flagellar motor and the molecular basis for rotational switching. Nature 466, 996–1000 (2010).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  36. Minamino, T. et al. Structural insight into the rotational switching mechanism of the bacterial flagellar motor. PLoS Biol. 9, e1000616 (2011).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  37. Sze, C. W. et al. Study of the response regulator Rrp1 reveals its regulatory role in chitobiose utilization and virulence of Borrelia burgdorferi. Infect. Immun. 81, 1775–1787 (2013).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  38. Motaleb, M. A., Pitzer, J. E., Sultan, S. Z. & Liu, J. A novel gene inactivation system reveals altered periplasmic flagellar orientation in a Borrelia burgdorferi fliL mutant. J. Bacteriol. 193, 3324–3331 (2011).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  39. Mastronarde, D. N. Automated electron microscope tomography using robust prediction of specimen movements. J. Struct. Biol. 152, 36–51 (2005).

    Article  PubMed  Google Scholar 

  40. Eisenstein, F., Danev, R. & Pilhofer, M. Improved applicability and robustness of fast cryo-electron tomography data acquisition. J. Struct. Biol. 208, 107–114 (2019).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  41. Zheng, S. Q. et al. MotionCor2: anisotropic correction of beam-induced motion for improved cryo-electron microscopy. Nat. Methods 14, 331–332 (2017).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  42. Kremer, J. R., Mastronarde, D. N. & McIntosh, J. R. Computer visualization of three-dimensional image data using IMOD. J. Struct. Biol. 116, 71–76 (1996).

    Article  CAS  PubMed  Google Scholar 

  43. Zhang, K. Gctf: real-time CTF determination and correction. J. Struct. Biol. 193, 1–12 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  44. Zhu, S., Qin, Z., Wang, J., Morado, D. R. & Liu, J. In situ structural analysis of the spirochetal flagellar motor by cryo-electron tomography. Methods Mol. Biol. 1593, 229–242 (2017).

    Article  CAS  PubMed  Google Scholar 

  45. Winkler, H. 3D reconstruction and processing of volumetric data in cryo-electron tomography. J. Struct. Biol. 157, 126–137 (2007).

    Article  CAS  PubMed  Google Scholar 

  46. Winkler, H. et al. Tomographic subvolume alignment and subvolume classification applied to myosin V and SIV envelope spikes. J. Struct. Biol. 165, 64–77 (2009).

    Article  CAS  PubMed  Google Scholar 

  47. Liu, J., Wright, E. R. & Winkler, H. in Methods in Enzymology Vol. 483 (ed. Jensen, G. J.) 267–290 (Academic Press, 2010).

  48. Notti, R. Q., Bhattacharya, S., Lilic, M. & Stebbins, C. E. A common assembly module in injectisome and flagellar type III secretion sorting platforms. Nat. Commun. 6, 7125 (2015).

    Article  PubMed  Google Scholar 

  49. Brown, P. N., Mathews, M. A. A., Joss, L. A., Hill, C. P. & Blair, D. F. Crystal structure of the flagellar rotor protein FliN from Thermotoga maritima. J. Bacteriol. 187, 2890–2902 (2005).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  50. Ahn, D.-R., Song, H., Kim, J., Lee, S. & Park, S. The crystal structure of an activated Thermotoga maritima CheY with N-terminal region of FliM. Int. J. Biol. Macromol. 54, 76–83 (2013).

    Article  CAS  PubMed  Google Scholar 

  51. Roy, A., Kucukural, A. & Zhang, Y. I-TASSER: a unified platform for automated protein structure and function prediction. Nat. Protoc. 5, 725–738 (2010).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  52. Yang, J. et al. The I-TASSER Suite: protein structure and function prediction. Nat. Methods 12, 7–8 (2015).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  53. Yang, J. & Zhang, Y. I-TASSER server: new development for protein structure and function predictions. Nucleic Acids Res. 43, W174–W181 (2015).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  54. Pettersen, E. F. et al. UCSF Chimera—a visualization system for exploratory research and analysis. J. Comput. Chem. 25, 1605–1612 (2004).

    Article  CAS  PubMed  Google Scholar 

  55. Lyskov, S. & Gray, J. J. The RosettaDock server for local protein–protein docking. Nucleic Acids Res. 36, W233–W238 (2008).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  56. Afonine, P. V., Grosse-Kunstleve, R. W., Adams, P. D. & Urzhumtsev, A. Bulk-solvent and overall scaling revisited: faster calculations, improved results. Acta Crystallogr. D Biol. Crystallogr. 69, 625–634 (2013).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  57. Goddard, T. D. et al. UCSF ChimeraX: meeting modern challenges in visualization and analysis. Protein Sci. 27, 14–25 (2018).

    Article  CAS  PubMed  Google Scholar 

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Acknowledgements

We thank M. Manson, J. Radolf, S. Kojima and M. Homma for critical reading and suggestions. This work was supported by grants from the National Institute of Allergy and Infectious Diseases (R01AI087946, R01AI078958, R01AI132818 and R01AI59048) and the National Institute of Dental and Craniofacial Research (R01DE023080). This work is dedicated to the memory of Professor Fanghua Li, who was an incredible scientist and a trusted mentor for Y.C., J.L. and many others in the field of electron microscopy.

Author information

Author notes

  1. Xiaowei Zhao

    Present address: Howard Hughes Medical Institute, Janelia Research Campus, Ashburn, VA, USA

  2. These authors contributed equally: Yunjie Chang, Kai Zhang.

Authors and Affiliations

  1. Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT, USA

    Yunjie Chang, Brittany L. Carroll & Jun Liu

  2. Microbial Sciences Institute, Yale University, West Haven, CT, USA

    Yunjie Chang, Brittany L. Carroll & Jun Liu

  3. Philips Institute for Oral Health Research, Virginia Commonwealth University, Richmond, VA, USA

    Kai Zhang & Chunhao Li

  4. Department of Pathology and Laboratory Medicine, University of Texas Health Science Center, Houston, TX, USA

    Xiaowei Zhao & Steven J. Norris

  5. Department of Microbiology, Immunology, and Cell Biology, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, USA

    Nyles W. Charon

  6. Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC, USA

    Md A. Motaleb

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Contributions

J.L. and C.L. conceived the project. Y.C. performed cryo-ET experiments, data analysis, modeling and wrote the manuscript draft. K.Z. performed genetic and biochemical experiments and analysis. B.L.C. and X.Z. contributed structural analysis. J.L. and C.L. supervised all work. M.A.M., S.J.N. and N.W.C. provided B. burgdorferi strains. Y.C., C.L. and J.L. prepared the manuscript with input from all authors.

Corresponding authors

Correspondence to Chunhao Li or Jun Liu.

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Extended data

Extended Data Fig. 1 Swimming motility modes and flagellar switching in E. coli and B. burgdorferi.

a, b, Cartoon of the swimming motility modes in E. coli: run and tumble. c, The motor rotates CCW as a default state. d, When the level of CheY-P becomes high enough, CheY-P binds to the C-ring, and the motor switches to CW rotation. The chemotaxis protein CheZ dephosphorylates CheY-P to return the motor to CCW rotation. e, f, Swimming motility modes in B. burgdorferi: run and flex. Periplasmic flagella (PF) are located between the inner membrane (IM) and outer membrane (OM). The flagellar motors are attached near each cell pole. Spirochetes run when the anterior flagella rotate CCW and the posterior flagella rotate CW (e). When the flagella at both poles rotate in the same direction (CW), the spirochetes flex in place and fail to move translationally. The swimming motility of B. burgdorferi is also controlled by a chemotaxis system. The homologs of CheY and CheZ in B. burgdorferi are CheY3 and CheX.

Extended Data Fig. 2 Cryo-ET imaging of the flagellar motors in ∆cheX and ∆cheY3 mutants.

a, A representative tomographic section from a ∆cheX cell tip reconstruction. Outer membrane (OM), inner membrane (IM), peptidoglycan layer (PG), and motors are clearly resolved in the tomogram. b, A representative section of a tomogram from a ∆cheY3 cell tip. Multiple motors with different orientations can be found at the cell tip. The insertions in (a, b) are the dark-field images showing a ∆cheX cell constantly flexing and a constantly running ∆cheY3 cell, respectively. c, A medial cross-section of an averaged map of the ∆cheX motor. d, The unrolled map refined using the stator region densities shows 16 stator complexes are embedded in the inner membrane (IM), while the C-ring subunits are unresolved due to symmetry mismatch between the C-ring and the stator. e, The unrolled map refined using the C-ring region densities shows 46-fold symmetric features, while the stator becomes blurry. Scale bar, 20 nm.

Extended Data Fig. 3 Comparison between in situ stator complex and the purified stator components.

a, Structure of purified MotA complex from A. aeolicus resolved by single particle EM (EMD 3417)27. b, The in situ stator complex in the ∆cheX motor has a bell-shaped structure embedded in the inner membrane (IM) and a periplasmic domain. The top part of the periplasmic domain matches well with the crystal structure of the S. enterica MotB periplasmic domain (PDB 2ZVY)28 (middle panel). The bell-shaped structure has similar size and shape as the structure of EMD 3417 (right panel). c, The in situ stator complex in the ∆cheY3-Class-2 motor is similar to that in the ∆cheX motor.

Extended Data Fig. 4 Schematic diagram for the in-frame replacement of cheX-cheY3 genes with cheY3-gfp and FLAG affinity purification using FLAG-FliM/FliN to pull down HisCheY3/CheY3*.

a, aadA, a streptomycin resistance gene was used as a selection marker. pcheX(F) and GFP (R) are oligonucleotide primers utilized to verify the occurrence of the allelic exchange of the recombinant construct (bottom) into the targeted region in the B. burgdorferi chromosome (top). b, Ni-NTA affinity purification using FLAG-tagged FliM (FliM-FLAG) and FLAG-tagged FliN (FliN-FLAG) to pull down HisCheY3 or HisCheY3* (CheY3D79A), respectively. HisCheY3 was co-purified with FliM-FLAG (b), but not with FliN-FLAG c, suggesting that CheY3 does not bind on FliN. In contrast, more HisCheY3 protein was co-purified with FliM-FLAG with acetyl phosphate (b), and HisCheY3* was not co-purified with FliM-FLAG (b) or FliN-FLAG (c). These results indicate that CheY3 binds to FliM protein in a phosphorylation-dependent manner.

Extended Data Fig. 5 Motor structures in constantly running ∆cheY3 cells.

a, A medial cross-section of an averaged structure in ∆cheY3 B. burgdorferi cell. b, c, Cross-sections show the stator ring and the C-ring, respectively. d, Focused structure of the C-ring (unrolled along the central rod). Two distinct classes in the ∆cheY3 cells are named as ∆cheY3-Class-1 e-h, and ∆cheY3-Class-2 i-l. Class-1 and Class-2 account ~45% and ~55% of all the ∆cheY3 motors we used for current work, respectively. The stator structures in Class-1 and Class-2 f and j, are quite similar, while the C-ring subunits (compare h with l) are tilted in different directions.

Extended Data Fig. 6 Motors adopt distinct conformations at the two cell poles in the same ∆cheY3 cell.

a, A tomographic section from one cell tip showed in panel b. Scale bar, 200 nm. (b) An overview of one intact ∆cheY3 cell. Scale bar, 1 µm. c, A tomographic section from another tip of the same cell in panel b. Scale bar, 200 nm. The motors at each cell tip were aligned separately, then focused refined to the C-ring. d-f, The motors from one cell tip have CCW conformation. g-t, The motors from another tip appear to adopt CW conformation. j-l, Averaged structure from motors located at one tip of five cells shows a better structure with CCW conformation. m-o, Averaged structure from motors located at another tip of five cells shows a better structure with CW conformation.

Extended Data Fig. 7 CheY3-P binding triggers conformational change.

a-d, Comparison between the C-ring models before (grey, top left in each panel) and after (colored, top right in each panel) CheY3-P binding. e, The dash framed regions in panel a are overlapped to show their differences. The N-terminal domain of FliM (FliMN) folds out ~154˚ to interact with CheY3-P. f, Binding of CheY3-P induces ~27˚ tilt of the FliM middle domain (FliMM). g, h, FliG2 undergoes a large tilt and alters the interactions between FliG2 and MotA. The charged residues (Lys275, Arg292, Glu299, and Asp300) in the C-terminal domain of FliG2 (FliG2C) are colored in red.

Extended Data Fig. 8 Comparison of the C-ring structures in CCW and CW rotation.

a, b, Diameters of the FliG2C, FliM and FliN rings in the C-ring with CCW rotation (∆cheY3-class-2). c, d, Diameters of the FliG2, FliM and FliN rings in the C-ring with CW rotation (∆cheX).

Extended Data Fig. 9 Motility model for B. burgdorferi.

a, b, In the default state, the concentration of CheY3-P is low, and the cell runs. The motors at the anterior cell pole rotate CCW, and the motors at the posterior cell pole rotate CW. Binding of unidentified proteins (grey circles at the inner side of the C-ring) to the C-ring at the posterior cell pole likely changes the motor to a CW conformation. c, d, At high concentrations of CheY3-P, the CCW rotating motors switch to CW rotation, while the CW rotating motors keep turning CW. Thus, the motors at both cell poles rotate CW and the cell flexes. After the flex, the direction of flagellar rotation at the two poles can switch so that the cell reverses the direction of its run.

Supplementary information

Supplementary Information

Supplementary Table 1 and Fig. 1.

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Supplementary Video 1

∆cheX cells flex in the video.

Supplementary Video 2

A refined structure of the flagellar motor in the ∆cheX mutant.

Supplementary Video 3

∆cheY3 cells constantly run in the video.

Supplementary Video 4

One class average of the flagellar motor in the ∆cheY3 mutant.

Supplementary Video 5

Another class average of the flagellar motor in the ∆cheY3 mutant.

Supplementary Video 6

An animation showing flagellar rotational switching in the Lyme disease spirochete.

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Chang, Y., Zhang, K., Carroll, B.L. et al. Molecular mechanism for rotational switching of the bacterial flagellar motor. Nat Struct Mol Biol 27, 1041–1047 (2020). https://doi.org/10.1038/s41594-020-0497-2

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