Structure of the AAA protein Msp1 reveals mechanism of mislocalized membrane protein extraction
- Howard Hughes Medical Institute, University of California, San Francisco, United States
- University of California, San Francisco, United States
Abstract
The AAA protein Msp1 extracts mislocalized tail-anchored membrane proteins and targets them for degradation, thus maintaining proper cell organization. How Msp1 selects its substrates and firmly engages them during the energetically unfavorable extraction process remains a mystery. To address this question, we solved cryo-EM structures of Msp1-substrate complexes at near-atomic resolution. Akin to other AAA proteins, Msp1 forms hexameric spirals that translocate substrates through a central pore. A singular hydrophobic substrate recruitment site is exposed at the spiral's seam, which we propose positions the substrate for entry into the pore. There, a tight web of aromatic amino acids grips the substrate in a sequence-promiscuous, hydrophobic milieu. Elements at the intersubunit interfaces coordinate ATP hydrolysis with the subunits' positions in the spiral. We present a comprehensive model of Msp1's mechanism, which follows general architectural principles established for other AAA proteins yet specializes Msp1 for its unique role in membrane protein extraction.
Data availability
All data needed to evaluate the conclusions in the paper are present in the paper and/or the supplementary materials. The atomic models were deposited in the protein data bank under the accession codes 6PDW, 6PDY and 6PE0; the associated cryo-EM maps were deposited in the electron microscopy data bank (EMDB) under the accession codes EMD-20318, EMD-20319 and EMD-20320
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Msp1-substrate complex in closed conformationProtein Data Bank, 6PDW.
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Msp1-substrate complex in open conformationProtein Data Bank, 6PDY.
Article and author information
Author details
Funding
National Institutes of Health (R01GM032384)
- Peter Walter
National Institutes of Health (R01GM032384)
- Lan Wang
Howard Hughes Medical Institute
- Peter Walter
Damon Runyon Cancer Research Foundation (DRG-2312-17)
- Lan Wang
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2020, Wang 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 the AAA protein Msp1 reveals mechanism of mislocalized membrane protein extraction
eLife 9:e54031.
https://doi.org/10.7554/eLife.54031
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