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Updated: Jul 21, 2025

Reconstitution of Msp1 Extraction Activity with Fully Purified Components
Published on: August 10, 2021
The AAA+ protein Msp1 recognizes substrates by a hydrophobic mismatch
Heidi L Fresenius1, Deepika Gaur1,2, Baylee Smith1,2
1Previously at University of Toledo, Department of Chemistry & Biochemistry.
Msp1 protein extracts misfolded membrane proteins by recognizing hydrophobic mismatches with the lipid bilayer. This extraction process is the rate-limiting step in Msp1
Area of Science:
- Cellular Biology
- Protein Quality Control
- Membrane Protein Biology
Background:
- Protein quality control involves removing aberrant membrane proteins from lipid bilayers.
- Dysfunctional protein removal is linked to neurodegenerative diseases and cancer.
- Msp1, a AAA+ ATPase, removes mistargeted proteins from the outer mitochondrial membrane.
Purpose of the Study:
- To elucidate the mechanism of Msp1 substrate recognition and extraction.
- To investigate the role of the lipid bilayer in Msp1-mediated membrane protein extraction.
Main Methods:
- Development of a quantitative and selective Msp1 extraction assay.
- Systematic modification of Msp1 substrates and the lipid environment.
- Analysis of substrate hydrophobic mismatch and lipid bilayer interactions.
Main Results:
- Msp1 recognizes substrates via a hydrophobic mismatch between the transmembrane domain (TMD) and the lipid bilayer.
- The rate-limiting step of Msp1 activity is the extraction of the substrate TMD from the lipid bilayer.
- The lipid bilayer significantly influences AAA+ mediated membrane protein extraction.
Conclusions:
- Msp1 utilizes a hydrophobic mismatch mechanism for substrate selection.
- Lipid bilayer properties are critical determinants of Msp1 efficiency.
- Findings provide fundamental insights into AAA+ protein function in membrane protein homeostasis.
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