HspQ Functions as a Unique Specificity-Enhancing Factor for the AAA+ Lon Protease.

Area of Science:

• Molecular Biology
• Protease Function
• Protein Homeostasis

Background:

• AAA+ Lon protease is vital for protein homeostasis across species.
• Lon protease plays roles in bacterial pathogenesis and human diseases.
• Understanding Lon's substrate selectivity is key to its biological functions.

Purpose of the Study:

• To elucidate the mechanism of substrate recognition and degradation by Lon protease.
• To identify novel substrates and regulators of Lon protease activity.
• To investigate the role of HspQ in Lon protease function.

Main Methods:

• Biochemical assays to study protein-protein interactions.
• Substrate degradation assays.
• Structural analysis of Lon-HspQ complex.

Main Results:

• HspQ identified as a novel Lon protease substrate and allosteric activator.
• Lon protease recognizes HspQ via a C-terminal degron and its native structure.
• HspQ binding allosterically activates Lon protease, enhancing degradation of multiple substrates.
• Two distinct substrate recognition sites on Lon protease identified: one for direct binding and one allosteric site modulated by HspQ.

Conclusions:

• HspQ represents a unique specificity-enhancing factor for Lon protease.
• Lon protease utilizes a novel regulatory mechanism involving an allosteric site activated by HspQ.
• This mechanism allows for temporally enhanced substrate selectivity by Lon protease, impacting protein homeostasis.