ClpS Directs Degradation of N-Degron Substrates With Primary Destabilizing Residues in Mycolicibacterium smegmatis

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Drug-resistant tuberculosis poses a significant global health challenge.
• The mycobacterial ClpC1P1P2 protease is a potential target for new antibiotics.
• Understanding the protease's cellular function requires knowledge of its substrates.

Purpose of the Study:

• To investigate the role of mycobacterial ClpS in the N-degron pathway.
• To determine how ClpS directs proteolysis by the ClpC1P1P2 protease in Mycolicibacterium smegmatis.

Main Methods:

• Binding assays to assess ClpS interaction with destabilizing residues.
• Conformational analysis of ClpS upon N-degron binding.
• Proteolytic reporter assays in M. smegmatis to evaluate substrate degradation.

Main Results:

• Mycobacterial ClpS binds primary N-degrons (Leu, Phe, Tyr, Trp) with moderate affinity.
• N-degron binding enhances ClpS-ClpC1 interaction affinity by approximately 30-fold.
• Substrates with primary N-degrons are degraded, but secondary N-degrons appear absent in mycobacteria.

Conclusions:

• ClpS is essential for substrate specificity in the mycobacterial N-degron pathway.
• The findings provide a mechanism for prioritizing N-degron proteolysis when substrates are abundant.
• This research offers insights for developing improved Clp protease inhibitors against drug-resistant tuberculosis.