A structural model of flagellar filament switching across multiple bacterial species
Fengbin Wang, Andrew M. Burrage, Sandra Postel, Reece E. Clark, Albina Orlova, Eric J. Sundberg, Daniel B. Kearns & Edward H. Egelman
Nature Communications 8, Article number: 960 (2017)
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Bacterial structural biologyCellular motility Cryoelectron microscopy Supramolecular assembly
Received: 05 July 2017 Accepted: 15 August 2017 Published online: 16 October 2017
Abstract
The bacterial flagellar filament has long been studied to understand how a polymer composed of a single protein can switch between different supercoiled states with high cooperativity. Here we present near-atomic resolution cryo-EM structures for flagellar filaments from both Gram-positive Bacillus subtilis and Gram-negative Pseudomonas aeruginosa. Seven mutant flagellar filaments in B. subtilis and two in P. aeruginosa capture two different states of the filament. These reliable atomic models of both states reveal conserved molecular interactions in the interior of the filament among B. subtilis, P. aeruginosa and Salmonella enterica. Using the detailed information about the molecular interactions in two filament states, we successfully predict point mutations that shift the equilibrium between those two states. Further, we observe the dimerization of P. aeruginosa outer domains without any perturbation of the conserved interior of the filament. Our results give new insights into how the flagellin sequence has been “tuned” over evolution.
Acknowledgements
This work was supported by NIH GM122510 (to E.H.E.) and GM093030 (to D.B.K.). The cryo-EM work was conducted at the Molecular Electron Microscopy Core facility at the University of Virginia, which is supported by the School of Medicine and built with NIH grant G20-RR31199. The Titan Krios and Falcon II direct electron detector within the Core were purchased with NIH SIG S10-RR025067 and S10-OD018149, respectively. We thank Dr. Zhangli Su for helpful edits of the manuscript.
Author information
Author notes
Fengbin Wang and Andrew M. Burrage contributed equally to this work.
Affiliations
Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
Fengbin Wang, Albina Orlova & Edward H. Egelman
Department of Biology, Indiana University, Bloomington, IN, 47305, USA
Andrew M. Burrage, Reece E. Clark & Daniel B. Kearns
Institute of Human Virology and University of Maryland School of Medicine, Baltimore, MD, 21201, USA
Sandra Postel & Eric J. Sundberg
Departments of Medicine and of Microbiology & Immunology, University of Maryland School of Medicine, Baltimore, 21201, MD, USA
Eric J. Sundberg
Contributions
A.M.B. performed site directed mutagenesis, phenotyping, and prepared the B. subtilis filament samples; R.E.C. screened for randomly generated non-motile alleles of B. subtilis hag and identified straight filament mutants; S.P. prepared the P. aeruginosa filament samples; A.O. and F.W. collected cryo-EM data; F.W. and E.H.E. performed image processing; F.W. did the structural modeling; F.W., A.M.B. and E.H.E. prepared figures; F.W. and E.H.E. wrote the manuscript; E.H.E., E.J.S. and D.B.K. conceived the study.
Competing interests
The authors declare no competing financial interests.
Corresponding author
Correspondence to Edward H. Egelman.
