Structural insights into the mechanism of protein transport by the Type 9 Secretion System translocon

Lauber, Frédéric;Deme, Justin C.;Liu, Xiaolong;Kjær, Andreas;Berks, Ben C.;et.al.
(2024) Nature Microbiology — Vol. 9, n° 4, p. 1089-1102 (2024)

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Authors
  • Lauber, Frédéricorcid-logoUCLouvain
    Co-first author
  • Deme, Justin C.orcid-logoCenter for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD, USA
    Co-first author
  • Liu, XiaolongDepartment of Biochemistry, University of Oxford, Oxford, UK
    Author
  • Kjær, AndreasDepartment of Biochemistry, University of Oxford, Oxford, UK
    Author
  • Berks, Ben C.orcid-logoDepartment of Biochemistry, University of Oxford, Oxford, UK
    Author
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Abstract
Secretion systems are protein export machines that enable bacteria to exploit their environment through the release of protein effectors. The Type 9 Secretion System (T9SS) is responsible for protein export across the outer membrane (OM) of bacteria of the phylum Bacteroidota. Here we trap the T9SS of Flavobacterium johnsoniae in the process of substrate transport by disrupting the T9SS motor complex. Cryo-EM analysis of purified substrate-bound T9SS translocons reveals an extended translocon structure in which the previously described translocon core is augmented by a periplasmic structure incorporating the proteins SprE, PorD and a homologue of the canonical periplasmic chaperone Skp. Substrate proteins bind to the extracellular loops of a carrier protein within the translocon pore. As transport intermediates accumulate on the translocon when energetic input is removed, we deduce that release of the substrate–carrier protein complex from the translocon is the energy-requiring step in T9SS transport.
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Lauber, F., Deme, J. C., Liu, X., Kjær, A., Miller, H. L., Alcock, F., Lea, S. M., & Berks, B. C. (2024). Structural insights into the mechanism of protein transport by the Type 9 Secretion System translocon. Nature Microbiology, 9(4), 1089-1102. https://doi.org/10.1038/s41564-024-01644-7 (Original work published 2024)