The CssRS two-component regulatory system controls a general secretion stress response in Bacillus subtilis

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Bacillus species secrete enzymes and biopharmaceuticals, necessitating protein quality control mechanisms.
• The CssRS two-component system regulates Bacillus subtilis cleaning proteases HtrA and HtrB.
• Previous understanding linked this stress response primarily to alpha-amylase production.

Purpose of the Study:

• To determine if protein translocation across the membrane is required for the secretion stress response.
• To investigate if heterologous secretory proteins can trigger this response.
• To assess the relationship between production levels, protein degradation, and stress response intensity.

Main Methods:

• Utilizing Bacillus subtilis as a model organism.
• Employing high-level production of homologous (AmyQ alpha-amylase) and heterologous secretory proteins (lipase A, human interleukin-3).
• Comparing stress response intensity with protein production levels and analyzing the impact of extracellular protease degradation.

Main Results:

• The CssRS-dependent secretion stress response is a general response activated by both homologous and heterologous secretory proteins.
• Membrane translocation of secretory proteins is essential to elicit this response, as shown with a non-translocated AmyQ variant.
• Stress response intensity correlates only partly with production levels and is minimally affected by degradation of proteins like human interleukin-3.

Conclusions:

• The Bacillus subtilis secretion stress response is a general mechanism triggered by translocated proteins.
• Protein translocation, not just production level, is key to activating the CssRS-mediated stress response.
• Extracellular degradation impacts protein yield but not significantly the secretion stress response intensity.