Structures of the ATP-fueled ClpXP proteolytic machine bound to protein substrate
- Massachusetts Institute of Technology, United States
- Harvard Medical School, United States
- Howard Hughes Medical Institute, Harvard Medical School, United States
Abstract
ClpXP is an ATP-dependent protease in which the ClpX AAA+ motor binds, unfolds, and translocates specific protein substrates into the degradation chamber of ClpP. We present cryo-EM studies of the E. coli enzyme that show how asymmetric hexameric rings of ClpX bind symmetric heptameric rings of ClpP and interact with protein substrates. Subunits in the ClpX hexamer assume a spiral conformation and interact with two-residue segments of substrate in the axial channel, as observed for other AAA+ proteases and protein-remodeling machines. Strictly sequential models of ATP hydrolysis and a power stroke that moves two residues of the substrate per translocation step have been inferred from these structural features for other AAA+ unfoldases, but biochemical and single-molecule biophysical studies indicate that ClpXP operates by a probabilistic mechanism in which five to eight residues are translocated for each ATP hydrolyzed. We propose structure-based models that could account for the functional results.
Data availability
PDB files for the structures determined here have been deposited in the PDB under accession codes 6PPE, 6PP8, 6PP7, 6PP6, 6PP5, 6POS, 6POD, 6PO3, and 6PO1.
Article and author information
Author details
Stephen C Harrison
Funding
National Institutes of Health (GM-101988)
- Robert T Sauer
Howard Hughes Medical Institute
- Tania A Baker
- Stephen C Harrison
National Institutes of Health (5T32GM-007287)
- Tristan A Bell
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2020, Fei 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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Structures of the ATP-fueled ClpXP proteolytic machine bound to protein substrate
eLife 9:e52774.
https://doi.org/10.7554/eLife.52774
