Article | Published:

Nucleation and growth of a bacterial functional amyloid at single-fiber resolution

Nature Chemical Biology volume 13, pages 902908 (2017) | Download Citation

Abstract

Curli are functional amyloids produced by proteobacteria like Escherichia coli as part of the extracellular matrix that holds cells together into biofilms. The molecular events that occur during curli nucleation and fiber extension remain largely unknown. Combining observations from curli amyloidogenesis in bulk solutions with real-time in situ nanoscopic imaging at the single-fiber level, we show that curli display polar growth, and we detect two kinetic regimes of fiber elongation. Single fibers exhibit stop-and-go dynamics characterized by bursts of steady-state growth alternated with periods of stagnation. At high subunit concentrations, fibers show constant, unperturbed burst growth. Curli follow a one-step nucleation process in which monomers contemporaneously fold and oligomerize into minimal fiber units that have growth characteristics identical to those of the mature fibrils. Kinetic data and interaction studies of curli fibrillation in the presence of the natural inhibitor CsgC show that the inhibitor binds curli fibers and predominantly acts at the level of fiber elongation.

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Acknowledgements

M.S. and N.V.G. acknowledge financial support by the FWO under projects G0H5316N and 1516215N, respectively. H.R. acknowledges financial support by VIB project grant PRJ9 and ERC grant 649082 BAS-SBBT. I.V.B. is a recipient of a PhD fellowship by the IWT. Work at the Université Catholique de Louvain was supported by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement no. 693630), the National Fund for Scientific Research (FNRS) and the FNRS-WELBIO (grant no. WELBIO-CR-2015A-05).

Author information

Author notes

    • Mike Sleutel
    • , Imke Van den Broeck
    •  & Nani Van Gerven

    These authors contributed equally to this work.

Affiliations

  1. Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium.

    • Mike Sleutel
    • , Imke Van den Broeck
    • , Nani Van Gerven
    • , Wim Jonckheere
    •  & Han Remaut
  2. Structural and Molecular Microbiology, Structural Biology Research Center, VIB, Brussels, Belgium.

    • Mike Sleutel
    • , Imke Van den Broeck
    • , Nani Van Gerven
    • , Wim Jonckheere
    •  & Han Remaut
  3. Institute of Life Sciences, Université Catholique de Louvain, Louvain-la-Neuve, Belgium.

    • Cécile Feuillie
    • , Claire Valotteau
    •  & Yves F Dufrêne
  4. Walloon Excellence in Life Sciences and Biotechnology (WELBIO), Belgium.

    • Yves F Dufrêne

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Contributions

I.V.B., W.J. and N.V.G. produced protein samples, performed bulk fibrillation, CsgC activity experiments, and TEM. I.V.B., N.V.G. and M.S. performed the biochemical assays. M.S. performed and analyzed AFM measurements with help from C.F., C.V. and Y.F.D. M.S. and H.R. supervised the study, analyzed data and wrote the paper, with contributions from all authors.

Competing interests

N.V.G. and H.R. are inventors on PCT/EP2014/079319, describing the use of amyloid peptides for protein display.

Corresponding authors

Correspondence to Mike Sleutel or Han Remaut.

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DOI

https://doi.org/10.1038/nchembio.2413

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