Structure of a AAA+ unfoldase in the process of unfolding substrate
- The Hospital for Sick Children Research Institute, Canada
- University of Toronto, Canada
Abstract
AAA+ unfoldases are thought to unfold substrate through the central pore of their hexameric structures, but how this process occurs is not known. VAT, the Thermoplasma acidophilum homologue of eukaryotic CDC48/p97, works in conjunction with the proteasome to degrade misfolded or damaged proteins. We show that in the presence of ATP, VAT with its regulatory N-terminal domains removed unfolds other VAT complexes as substrate. We captured images of this transient process by electron cryomicroscopy (cryo-EM) to reveal the structure of the substrate-bound intermediate. Substrate binding breaks the six-fold symmetry of the complex, allowing five of the six VAT subunits to constrict into a tight helix that grips an ~80 Å stretch of unfolded protein. The structure suggests a processive hand-over-hand unfolding mechanism, where each VAT subunit releases the substrate in turn before re-engaging further along the target protein, thereby unfolding it.
Data availability
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VCP like ATPase from T. acidophilum (VAT) - Conformation 1Publicly available at the EMBL-EMD Protein Data Bank in Europe (accession no. EMD-8658).
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VCP like ATPase from T. acidophilum (VAT) - Substrate bound conformationPublicly available at the EMBL-EMD Protein Data Bank in Europe (accession no. EMD-8659.
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VCP like ATPase from T. acidophilum (VAT) - Conformation 1Publicly available at the RCSB Protein Data Bank (accession no. 5VC7.
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VCP like ATPase from T. acidophilum (VAT) - Substrate bound conformationPublicly available at the RCSB Protein Data Bank (accession no. 5VCA).
Article and author information
Author details
Funding
Canadian Institutes of Health Research (MOP133408 MOP81294)
- John L Rubinstein
Natural Sciences and Engineering Research Council of Canada
- Zev A Ripstein
Canada Research Chairs
- John L Rubinstein
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2017, Ripstein et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Structure of a AAA+ unfoldase in the process of unfolding substrate
eLife 6:e25754.
https://doi.org/10.7554/eLife.25754
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