Summary auto-generated
This study used computer-aided two-dimensional protein gel electrophoresis to analyze the stress response in Bacillus subtilis. Researchers exposed wild-type and sigB mutant strains to various stresses including heat shock, salt, ethanol, oxidative stress, and glucose/phosphate starvation. They identified approximately 50 general stress proteins induced across multiple stress conditions. At least 42 of these required the alternative sigma factor σB for induction (class II proteins), while at least seven stress proteins remained inducible without σB (class III proteins), including ClpC, ClpP, Sod, AhpC, and AhpF. During stress, general stress proteins comprised up to 40% of total protein synthesis, demonstrating their importance. The researchers also identified stress-specific proteins induced only by particular conditions. Additionally, they identified subgroups of stress proteins subject to additional regulatory circuits beyond σB control, revealing a complex, finely-tuned stress response system. Computer analysis enabled quantitative measurement of protein synthesis rates under different physiological conditions.
Key findings
- At least 42 general stress proteins absolutely require sigma factor σB for induction, while at least 7 stress proteins remain stress-inducible without σB
- During stress conditions, general stress proteins constitute up to 40% of total protein synthesis, highlighting their physiological importance
- Multiple subgroups of stress proteins exist with additional regulatory circuits beyond σB control, including differential responses to glucose starvation, ethanol, salt stress, and oxidative stress
- Seven proteins including ClpC, ClpP, Sod, AhpC, and AhpF remain stress-inducible in sigB mutants, indicating σB-independent stress response mechanisms
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Abstract
A computer-aided analysis of high resolution two-dimensional polyacrylamide gels was used to investigate the changes in the protein synthesis profile in B. subtilis wild-type strains and sigB mutants in response to heat shock, salt and ethanol stress, and glucose of phosphate starvation. The data provided evidence that the induction of a least 42 general stress proteins absolutely required the alternative sigma factor sigmaB. However, at least seven stress proteins, among them ClpC, ClpP, Sod, AhpC and AhpF, remained stress-inducible in a sigB mutant. Such a detailed analysis also premitted the description of subgroups of general stress proteins which are subject to additional regulatory circuits, indicating a very thorough fine-tuning of this complex response. The relative synthesis rate of the general stress proteins constituted up to 40% of the total protein synthesis of stressed cells and thereby emphasizes the importance of the stress regulon. Besides the induction of these general or rather unspecific stress proteins, the induction of stress-specific proteins is shown and discussed.