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Cleavage site selection within a folded substrate by the ATP-dependent lon protease
Gabriela Ondrovicová1, Tong Liu, Kamalendra Singh
1Institute of Molecular Biology, Slovak Academy of Sciences, 84551 Bratislava, Slovak Republic.
The Journal of Biological Chemistry
|May 5, 2005
Summary
Mitochondrial Lon protease degrades folded proteins by initiating cleavage non-processively, unlike previously known mechanisms. This protease targets specific surface features before processively degrading the unfolded polypeptide chain.
Area of Science:
- Biochemistry and Molecular Biology
- Proteolysis Mechanisms
- Mitochondrial Protein Degradation
Background:
- ATP-dependent proteolysis typically requires substrate unfolding before hydrolysis.
- The role of mitochondrial Lon protease in degrading folded proteins was unclear.
- Understanding substrate recognition and cleavage initiation is crucial for proteolysis studies.
Purpose of the Study:
- To investigate the degradation mechanism of mitochondrial Lon protease.
- To determine if Lon can degrade folded proteins.
- To identify the initial cleavage sites and degradation process of Lon on specific mitochondrial substrates.
Main Methods:
- Utilized two mitochondrial substrates with known 3D structures: MPPalpha and StAR.
- Performed time-course analysis of Lon-mediated proteolysis.
- Identified and mapped generated peptides to substrate primary, secondary, and tertiary structures.
Main Results:
- Mitochondrial Lon protease degrades folded proteins, initiating cleavage non-processively.
- Initial cleavages occurred at solvent-accessible sites between hydrophobic amino acids on the protein surface.
- Subsequent degradation proceeded sequentially along the polypeptide chain after initial unfolding.
Conclusions:
- Mitochondrial Lon protease recognizes specific surface determinants or folds on substrates.
- Lon initiates proteolysis at accessible sites, leading to substrate unfolding.
- The unfolded polypeptides are then degraded processively by Lon.