Sequestration from Protease Adaptor Confers Differential Stability to Protease Substrate.
Jinki Yeom1, Kyle J Wayne1, Eduardo A Groisman2
1Department of Microbial Pathogenesis, Yale School of Medicine, 295 Congress Avenue, New Haven, CT 06536, USA.
Molecular Cell
|April 22, 2017
Summary
Salmonella
Area of Science:
- Bacterial protein degradation pathways
- Molecular mechanisms of gene regulation
Background:
- The N-end rule dictates protein stability based on N-terminal residues.
- Bacterial adaptor ClpS delivers N-terminally tagged substrates to the ClpAP protease for degradation.
- Understanding PhoP regulation is crucial for bacterial survival and virulence.
Purpose of the Study:
- To elucidate the mechanism by which the regulatory protein PhoP is degraded in Salmonella.
- To identify factors that regulate PhoP stability and its subsequent impact on gene expression.
- To investigate the role of the MgtC protein in PhoP proteolysis.
Main Methods:
- Investigated the interaction between Salmonella ClpS and the N-terminus of PhoP.
- Assessed the effect of MgtC on PhoP degradation by the ClpAP protease.
- Utilized site-directed mutagenesis to remove N-terminal residues of PhoP.
- Analyzed the transcriptional activity of PhoP-activated genes under different conditions.
Main Results:
- Salmonella ClpS binds to PhoP's N-terminus, targeting it for ClpAP-mediated degradation.
- The PhoP-activated protein MgtC competitively inhibits ClpS binding to PhoP, preventing degradation.
- MgtC's protective effect is specific to PhoP, not affecting other ClpS/ClpAP substrates.
- Deletion of PhoP's N-terminal five residues abolished the requirement for clpS and mgtC for stability.
- MgtC maintains PhoP protein levels, ensuring proper temporal transcription of PhoP-regulated genes.
Conclusions:
- A novel mechanism of substrate-specific protein stabilization is described, mediated by MgtC.
- MgtC acts as a specific inhibitor of PhoP degradation by the ClpS-ClpAP system.
- This regulatory pathway allows for precise control over PhoP levels and downstream gene expression in Salmonella.
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