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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.
Bernhardt et al. (Sat,) studied this question.