Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 104, Issue 16, Pages 6590-6595Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0701776104
Keywords
ClpP; regulated degradation; ClpX
Categories
Funding
- NIAID NIH HHS [R01 AI016892, AI-16892] Funding Source: Medline
- NIGMS NIH HHS [R01 GM049224, GM-49224, R01 GM049224-16] Funding Source: Medline
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Regulated proteolysis is required to execute many cellular programs. In Caulobacter crescentus, timely degradation of the master regulator CtrA by ClpXP protease is essential for cell-cycle progression and requires the colocalization of CtrA and RcdA. Here, we establish a biochemical framework to understand regulated proteolysis in C crescentus and show that RcdA is not an adaptor for CtrA degradation. CtrA is rapidly degraded without RcdA and is recognized with an affinity comparable with the best ClpXP substrates. In contrast, SspB alpha, the alpha-proteobacterial homolog of SspB, functions as an adaptor to enhance degradation of specific substrates. Cargo-free SspB alpha is also itself a substrate of ClpXP-mediated proteolysis. Thus, our analysis (i) reveals the consequences of both direct and adaptor-stimulated recognition in mediating substrate specificity in vitro, (ii) reveals a potential regulatory role of controlled adaptor stability, and (iii) suggests that cell-cycle regulation of CtrA stability depends on repression of its intrinsic degradation rather than adaptor-mediated enhancement.
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