Structural Basis of Protein Translocation by the Vps4-Vta1 AAA ATPase
- University of Utah School of Medicine, United States
Abstract
Many important cellular membrane fission reactions are driven by ESCRT pathways, which culminate in disassembly of ESCRT-III polymers by the AAA ATPase Vps4. We report a 4.3 Å resolution cryo-EM structure of the active Vps4 hexamer with its cofactor Vta1, ADP•BeFx, and an ESCRT-III substrate peptide. Four Vps4 subunits form a helix whose interfaces are consistent with ATP-binding, is stabilized by Vta1, and binds the substrate peptide. The fifth subunit approximately continues this helix but appears to be dissociating. The final Vps4 subunit completes a notched-washer configuration as if transitioning between the ends of the helix. We propose that ATP binding propagates growth at one end of the helix while hydrolysis promotes disassembly at the other end, so that Vps4 'walks' along ESCRT-III until it encounters the ordered N-terminal domain to destabilize the ESCRT-III lattice. This model may be generally applicable to other protein-translocating AAA ATPases.
Data availability
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Vps4-Vta1 complexPublicly available at the RCSB Protein Data Bank (accession no: 5UIE).
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Vps4-Vta1 complexPublicly available at the EMBL-EBI Protein Data Bank (accession no: EMD-8549).
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Vps4-Vta1 complex_sharpened mapPublicly available at the EMBL-EBI Protein Data Bank (accession no: EMD-8550).
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Vps4-HCP hexamerPublicly available at the EMBL-EBI Protein Data Bank (accession no: EMD-8551).
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Vps4-Vta1 complex_VSL_APublicly available at the EMBL-EBI Protein Data Bank (accession no: EMD-8552).
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Vps4-Vta1 complex_VSL_BPublicly available at the EMBL-EBI Protein Data Bank (accession no: EMD-8553).
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Vps4-Vta1 complex_VSL_CPublicly available at the EMBL-EBI Protein Data Bank (accession no: EMD-8554).
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Vps4-Vta1 complex_VSL_DPublicly available at the EMBL-EBI Protein Data Bank (accession no: EMD-8555).
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Vps4-Vta1 complex_VSL_EPublicly available at the EMBL-EBI Protein Data Bank (accession no: EMD-8556).
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Vps4-Vta1 complex_VSL_FPublicly available at the EMBL-EBI Protein Data Bank (accession no: EMD-8557).
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Vps4-Vta1 complex, State 3 of subunitFPublicly available at the EMBL-EBI Protein Data Bank (accession no: EMD-8570).
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Vps4-Vta1 complex, State 2 of subunitFPublicly available at the EMBL-EBI Protein Data Bank (accession no: EMD-8571).
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Vps4-Vta1 complex, State 1 of subunitFPublicly available at the EMBL-EBI Protein Data Bank (accession no: EMD-8572).
Article and author information
Author details
Wesley I Sundquist
Christopher P Hill
Funding
National Institutes of Health (P50 GM082545)
- Nicole Monroe
- Han Han
- Peter S Shen
- Wesley I Sundquist
- Christopher P Hill
National Institutes of Health (Microbial Pathogenesis Training Grant T32 AI055434)
- Nicole Monroe
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Reviewing Editor
- Sriram Subramaniam, National Cancer Institute, United States
Version history
- Received: December 21, 2016
- Accepted: April 4, 2017
- Accepted Manuscript published: April 5, 2017 (version 1)
- Version of Record published: May 2, 2017 (version 2)
Copyright
© 2017, Monroe 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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Structural Basis of Protein Translocation by the Vps4-Vta1 AAA ATPase
eLife 6:e24487.
https://doi.org/10.7554/eLife.24487
Further reading
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- Biochemistry and Chemical Biology
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Protein homeostasis (proteostasis) deficiency is an important contributing factor to neurological and metabolic diseases. However, how the proteostasis network orchestrates the folding and assembly of multi-subunit membrane proteins is poorly understood. Previous proteomics studies identified Hsp47 (Gene: SERPINH1), a heat shock protein in the endoplasmic reticulum lumen, as the most enriched interacting chaperone for gamma-aminobutyric acid type A (GABAA) receptors. Here, we show that Hsp47 enhances the functional surface expression of GABAA receptors in rat neurons and human HEK293T cells. Furthermore, molecular mechanism study demonstrates that Hsp47 acts after BiP (Gene: HSPA5) and preferentially binds the folded conformation of GABAA receptors without inducing the unfolded protein response in HEK293T cells. Therefore, Hsp47 promotes the subunit-subunit interaction, the receptor assembly process, and the anterograde trafficking of GABAA receptors. Overexpressing Hsp47 is sufficient to correct the surface expression and function of epilepsy-associated GABAA receptor variants in HEK293T cells. Hsp47 also promotes the surface trafficking of other Cys-loop receptors, including nicotinic acetylcholine receptors and serotonin type 3 receptors in HEK293T cells. Therefore, in addition to its known function as a collagen chaperone, this work establishes that Hsp47 plays a critical and general role in the maturation of multi-subunit Cys-loop neuroreceptors.
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Previously, Tuller et al. found that the first 30–50 codons of the genes of yeast and other eukaryotes are slightly enriched for rare codons. They argued that this slowed translation, and was adaptive because it queued ribosomes to prevent collisions. Today, the translational speeds of different codons are known, and indeed rare codons are translated slowly. We re-examined this 5’ slow translation ‘ramp.’ We confirm that 5’ regions are slightly enriched for rare codons; in addition, they are depleted for downstream Start codons (which are fast), with both effects contributing to slow 5’ translation. However, we also find that the 5’ (and 3’) ends of yeast genes are poorly conserved in evolution, suggesting that they are unstable and turnover relatively rapidly. When a new 5’ end forms de novo, it is likely to include codons that would otherwise be rare. Because evolution has had a relatively short time to select against these codons, 5’ ends are typically slightly enriched for rare, slow codons. Opposite to the expectation of Tuller et al., we show by direct experiment that genes with slowly translated codons at the 5’ end are expressed relatively poorly, and that substituting faster synonymous codons improves expression. Direct experiment shows that slow codons do not prevent downstream ribosome collisions. Further informatic studies suggest that for natural genes, slow 5’ ends are correlated with poor gene expression, opposite to the expectation of Tuller et al. Thus, we conclude that slow 5’ translation is a ‘spandrel’--a non-adaptive consequence of something else, in this case, the turnover of 5’ ends in evolution, and it does not improve translation.
