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Defining Substrate Specificities for Lipase and Phospholipase Candidates
Published on: November 23, 2016
The ClpP N-terminus coordinates substrate access with protease active site reactivity.
Laura D Jennings1, Jen Bohon, Mark R Chance
1Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
Biochemistry
|September 26, 2008
Summary
The ClpP N-terminus acts as a gate in energy-dependent protein degradation. Binding of ClpA opens this gate, facilitating substrate entry and degradation by the ClpAP machine.
Area of Science:
- Molecular Biology
- Biochemistry
- Protein Degradation Machinery
Background:
- Energy-dependent proteases like E. coli ClpAP rely on regulated interactions between ClpA and ClpP.
- The ClpP N-terminus is crucial for these interactions, but its dynamic behavior is not well understood.
Purpose of the Study:
- To investigate the conformational dynamics of the ClpP N-terminus during ClpAP complex function.
- To elucidate the role of the ClpP N-terminus in regulating substrate access and proteolysis.
Main Methods:
- Synchrotron hydroxyl radical footprinting to map solvent accessibility.
- Kinetic studies to analyze degradation rates and product formation.
- Site-directed mutagenesis to assess the impact of N-terminal deletions.
Main Results:
- The ClpP N-terminus becomes more solvent-exposed upon ClpA binding.
- Deletion of the ClpP N-terminus significantly increases the degradation rate of large peptides.
- N-terminal truncation leads to a stabilized acyl-enzyme intermediate, suggesting impaired hydrolysis.
Conclusions:
- The ClpP N-terminus functions as a gate controlling substrate entry into the ClpP active sites.
- ClpA binding opens this gate, enabling substrate processing.
- The N-terminal gate's closure is linked to acyl-enzyme hydrolysis, regulating the degradation cycle.
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