Blm10 binds to pre-activated proteasome core particles with open gate conformation

Area of Science:

• Molecular Biology
• Proteasome Function
• Enzyme Regulation

Background:

• The proteasome core particle (CP) is essential for protein degradation in eukaryotes.
• CP gate conformation (closed or open) regulates substrate access to the catalytic site.
• Blm10 is a known CP-binding protein.

Purpose of the Study:

• To investigate the interaction between Blm10 and the yeast proteasome core particle (CP).
• To determine how Blm10 binding affects CP gate conformation and proteolytic activity.
• To elucidate the regulatory role of Blm10 in CP activation.

Main Methods:

• Biochemical assays to assess peptide hydrolysis activity of Blm10-CP complexes.
• Analysis of CP assembly mutants and open gate mutants.
• Characterization of Blm10 binding to different CP conformations.

Main Results:

• Blm10 preferentially binds to pre-activated, open-gate CPs.
• Single-capped Blm10-CP complexes exhibit peptide hydrolysis activity.
• Blm10 sequesters disordered or constitutively active CPs into inactive double-capped Blm10(2)-CP complexes.
• Blm10 binding is conformation-dependent, distinguishing between open and closed gates.

Conclusions:

• Blm10 acts as a gatekeeper, distinguishing between different CP conformations.
• Blm10 regulates proteasome activity by modulating CP gate accessibility and stability.
• This interaction provides insights into the fine-tuning of proteasome-mediated protein degradation.