Studying chaperone-proteases using a real-time approach based on FRET.

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Chaperone-proteases are essential cellular machines responsible for regulated protein degradation.
• These complexes consist of a protease core and ATPase subunits that control substrate entry.
• Understanding their mechanism is crucial for comprehending protein homeostasis and disease.

Purpose of the Study:

• To develop and apply a real-time Förster Resonance Energy Transfer (FRET)-based method to probe chaperone-protease reaction cycles.
• To elucidate the mechanism of substrate processing by bacterial ClpAP and ClpXP complexes.
• To assess the broader applicability of the FRET system using archaeal proteasome models.

Main Methods:

• Development of a real-time FRET assay to monitor substrate unfolding, translocation, and degradation.
• Application of the FRET system to study bacterial ClpAP and ClpXP chaperone-protease complexes.
• Validation of the FRET system using the archaeal PAN-proteasome complex.

Main Results:

• The FRET system successfully monitored the chaperone-protease reaction cycle in real-time.
• Both ClpAP and ClpXP complexes exhibit a conserved mechanism involving rapid substrate unfolding and threading, followed by slower translocation.
• A transient compact substrate intermediate was observed near the chaperone-protease interface.
• Data support a mechanical unfolding model for ClpX and ClpA action.
• The FRET method demonstrated applicability to the archaeal PAN-proteasome.

Conclusions:

• Bacterial ClpAP and ClpXP chaperone-proteases share a common mechanism for protein degradation.
• The study provides evidence for mechanical unfolding as the mode of action for ClpX and ClpA.
• The developed FRET system is a versatile tool for studying diverse proteasome complexes, including eukaryotic ones.