Article | Published:

Structure of the T4 baseplate and its function in triggering sheath contraction

Nature volume 533, pages 346352 (19 May 2016) | Download Citation

Abstract

Several systems, including contractile tail bacteriophages, the type VI secretion system and R-type pyocins, use a multiprotein tubular apparatus to attach to and penetrate host cell membranes. This macromolecular machine resembles a stretched, coiled spring (or sheath) wound around a rigid tube with a spike-shaped protein at its tip. A baseplate structure, which is arguably the most complex part of this assembly, relays the contraction signal to the sheath. Here we present the atomic structure of the approximately 6-megadalton bacteriophage T4 baseplate in its pre- and post-host attachment states and explain the events that lead to sheath contraction in atomic detail. We establish the identity and function of a minimal set of components that is conserved in all contractile injection systems and show that the triggering mechanism is universally conserved.

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Accessions

Primary accessions

Electron Microscopy Data Bank

NCBI Reference Sequence

Data deposits

Cryo-EM maps have been deposited in the Electron Microscopy Data Bank under the following accession numbers: EMD-3374 and EMD-3396 for the pre-attachment and post-attachment baseplate, respectively, and EMD-3397, EMD-3392, EMD-3393, EMD-3394 and EMD-3395 for the locally masked reconstructions of the pre-attachment baseplate for the tail tube, inner, intermediate, upper and lower peripheral baseplate regions, respectively. Atomic coordinates have been deposited in the Protein Data Bank under the following accession numbers: 5IV5 and 5IV7 for the pre-attachment and post-attachment baseplate, respectively, and 4HRZ for the crystal structure of T4 gp25. The vector with the TEV-cleavable His–SlyD expression tag derived from pET-23d(+) (Novagen) has been deposited to the NCBI database under the accession number KU314761.

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Acknowledgements

We thank V. Mesyanshinov for developing the initial baseplate–tail tube complex purification protocol; C. Maillard for technical support; A. Brown for advice on structure refinement involving cryo-EM data; D. Demurtas for sample screening by negative stain EM; R. McLeod for help with data transfer; S. Nazarov, M. Plattner, and V. Kostyuchenko for discussions; and M. Basler for reading the manuscript. We acknowledge support from the EPFL SCITAS (high performance computing), the EPFL Centre for Interdisciplinary Electron Microscopy and the EPFL Proteomics Core Facility. The work was supported by the Swiss National Science Foundation grant 310030_144243.

Author information

Author notes

    • Christopher Browning

    Present address: Vertex Pharmaceuticals (Europe) Ltd, 86–88 Jubilee Avenue, Milton Park, Abingdon, Oxfordshire OX14 4RW, UK.

Affiliations

  1. École Polytechnique Fédérale de Lausanne (EPFL), BSP-415, 1015 Lausanne, Switzerland

    • Nicholas M. I. Taylor
    • , Nikolai S. Prokhorov
    • , Ricardo C. Guerrero-Ferreira
    • , Mikhail M. Shneider
    • , Christopher Browning
    •  & Petr G. Leiman
  2. Winogradsky Institute of Microbiology, Research Center of Biotechnology of the Russian Academy of Sciences, pr. 60-letiya Oktyabrya, 7 build. 2, 117312, Moscow, Russia

    • Nikolai S. Prokhorov
  3. Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Laboratory of Molecular Bioengineering, 16/10 Miklukho-Maklaya St., 117997 Moscow, Russia

    • Mikhail M. Shneider
  4. Center for Cellular Imaging and NanoAnalytics (C-CINA), Biozentrum, University of Basel, Mattenstrasse 26, 4058 Basel, Switzerland

    • Kenneth N. Goldie
    •  & Henning Stahlberg

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Contributions

N.M.I.T. purified the baseplates, calculated cryo-EM reconstructions, built and refined all atomic models, performed bioinformatic analyses and wrote the first draft of the paper. R.C.G.-F., N.M.I.T., K.N.G. and H.S. collected cryo-EM data. N.M.I.T. and N.S.P. designed, and N.S.P. performed, site-directed mutagenesis of T4 phage. M.M.S. designed, produced and analysed T6SS samples and T4 gp25. C.B. crystallized T4 gp25. P.G.L. solved the T4 gp25 structure, analysed the data from all sources, and integrated all the information into a single manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Petr G. Leiman.

Extended data

Supplementary information

PDF files

  1. 1.

    Supplementary Information

    This file contains a Supplementary Discussion, Supplementary Tables 1-5 and Supplementary Figure 1 (uncropped gels).

Videos

  1. 1.

    Structural transformation of the baseplate upon binding to the host membrane

    The intermediates were obtained by interpolating between the initial and final structure with the help of UCSF Chimera except for the motion and structure of the short tail fibers and the jump rope loop of gp7 (See text for details). The color code is as in Figure 1. NB: The conformational switch is irreversible and the reverse trajectories in this and all other animations are shown only for clarity of visualization.

  2. 2.

    Baseplate conformational switch is accompanied by the release of the hub-tube complex from the conserved wedge proteins gp25 (light green), gp53 (pink), gp6 (yellow and red), and gp7 (blue).

    Baseplate conformational switch is accompanied by the release of the hub-tube complex from the conserved wedge proteins gp25 (light green), gp53 (pink), gp6 (yellow and red), and gp7 (blue).

  3. 3.

    Transformation of the iris formed by the (gp6)2-gp7 heterotrimers and gp6 C-terminal dimers during the baseplate conformational switch. Gp6 is in yellow and red and gp7 is in blue.

    Transformation of the iris formed by the (gp6)2-gp7 heterotrimers and gp6 C-terminal dimers during the baseplate conformational switch. Gp6 is in yellow and red and gp7 is in blue.

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https://doi.org/10.1038/nature17971

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