An Adaptor Hierarchy Regulates Proteolysis during a Bacterial Cell Cycle

Area of Science:

• Bacteriology
• Molecular Biology
• Cell Biology

Background:

• Regulated protein degradation is vital for cellular processes, including the cell cycle.
• The ClpXP protease in Caulobacter crescentus degrades key proteins to drive cell-cycle progression.
• The precise mechanisms governing cell-cycle-dependent proteolysis by ClpXP are not fully understood.

Purpose of the Study:

• To elucidate the role of adaptor proteins in regulating ClpXP protease activity during the Caulobacter crescentus cell cycle.
• To uncover the hierarchical nature of adaptor assembly and its impact on substrate degradation.
• To identify novel cell-cycle-dependent substrates of the ClpXP protease.

Main Methods:

• Investigated the function of adaptor proteins CpdR, RcdA, and PopA in ClpXP-mediated proteolysis.
• Dissected the RcdA adaptor to identify substrate recognition elements.
• Utilized proteomic approaches to identify additional cell-cycle-dependent ClpXP substrates.

Main Results:

• Demonstrated an adaptor hierarchy controlling ClpXP substrate degradation.
• Showed that CpdR primes ClpXP, RcdA targets a second substrate class, and PopA targets a third class while inhibiting RcdA.
• Identified key substrate elements for RcdA recognition and discovered new cell-cycle-dependent ClpXP substrates.

Conclusions:

• Hierarchical adaptors and primed proteases orchestrate regulated proteolysis during bacterial cell-cycle progression.
• The adaptor hierarchy ensures substrate specificity and timely degradation, crucial for cell division.
• This study provides a framework for understanding complex proteolytic regulation in bacteria.