Proteasome in action: substrate degradation by the 26S proteasome

Area of Science:

• Cellular Biology
• Biochemistry
• Structural Biology

Background:

• The 26S proteasome is a crucial cellular machine responsible for protein degradation.
• Protein ubiquitination and the presence of disordered segments are key signals for substrate recognition.
• The 19S regulatory particle (RP) and 20S catalytic core (CP) form the functional proteasome.

Purpose of the Study:

• To review recent insights into the biochemical and structural mechanisms of substrate recognition and processing by the 26S proteasome.
• To elucidate the dynamic conformational changes of the proteasome during substrate engagement and degradation.

Main Methods:

• Literature review of biochemical and structural studies.
• Analysis of proteasome structure-function relationships.

Main Results:

• Resting proteasomes exhibit peripheral ubiquitin receptors and an open ATPase ring for substrate entry.
• Substrate binding induces RP contraction, ATPase engagement, and polypeptide unfolding for translocation.
• Rpn11 repositioning and ATPase-20S CP interaction facilitate gate opening and substrate processing.

Conclusions:

• The 26S proteasome employs dynamic conformational states for efficient substrate recognition, unfolding, and degradation.
• Understanding these mechanisms provides insight into protein homeostasis and disease-related pathways.