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Structural and energetic basis of folded-protein transport by the FimD usher

Nature volume 496, pages 243246 (11 April 2013) | Download Citation


Type 1 pili, produced by uropathogenic Escherichia coli, are multisubunit fibres crucial in recognition of and adhesion to host tissues1. During pilus biogenesis, subunits are recruited to an outer membrane assembly platform, the FimD usher, which catalyses their polymerization and mediates pilus secretion2. The recent determination of the crystal structure of an initiation complex provided insight into the initiation step of pilus biogenesis resulting in pore activation, but very little is known about the elongation steps that follow3. Here, to address this question, we determine the structure of an elongation complex in which the tip complex assembly composed of FimC, FimF, FimG and FimH passes through FimD. This structure demonstrates the conformational changes required to prevent backsliding of the nascent pilus through the FimD pore and also reveals unexpected properties of the usher pore. We show that the circular binding interface between the pore lumen and the folded substrate participates in transport by defining a low-energy pathway along which the nascent pilus polymer is guided during secretion.

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Protein Data Bank

Data deposits

The atomic coordinates and structure factors of FimD–FimC–FimF–FimG–FimH have been deposited in the Protein Data Bank under accession ID 4J3O.


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This work was funded by Medical Research Council grant 85602 to G.W. D.B. and E.P. are supported by grant P41 GM103533 from the National Institute of General Medical Studies at the US National Institutes of Health (NIH). S.J.H. was supported by grant AI029549 from the National Institute of Allergy and Infectious Disease at the NIH. We thank the staff of beamline ID23-1 at the European Synchrotron Radiation Facility, the staff of beamline IO2 at the Diamond Light source and A. Cole for technical assistance during data collection.

Author information

Author notes

    • Sebastian Geibel
    •  & Erik Procko

    These authors contributed equally to this work.


  1. Institute of Structural and Molecular Biology, University College London and Birkbeck College, Malet Street, London WC1E 7HX, UK

    • Sebastian Geibel
    •  & Gabriel Waksman
  2. The Howard Hughes Medical Institute and Department of Biochemistry, University of Washington, Seattle, Washington 98195, USA

    • Erik Procko
    •  & David Baker
  3. Center for Women’s Infectious Disease Research and Department of Molecular Microbiology, Washington University School of Medicine, St Louis, Missouri 63011, USA

    • Scott J. Hultgren


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S.G. and E.P. carried out the crystallographic and computational work, respectively. D.B. and G.W. supervised the work. S.G., E.P., D.B. and G.W. analysed the data. S.G., E.P., S.J.H., D.B. and G.W. wrote the paper.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to David Baker or Gabriel Waksman.

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    Supplementary Information

    This file contains Supplementary Methods, Supplementary Tables 1-2, Supplementary Figures 1-16 and Supplementary References.

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