The Escherichia coli sigma E-dependent extracytoplasmic stress response is controlled by the regulated proteolysis of an anti-sigma factor

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Abstract
The activity of the stress-responsive ς factor, ςE, is induced by the extracytoplasmic accumulation of misfolded or unfolded protein. The inner membrane protein RseA is the central regulatory molecule in this signal transduction cascade and acts as a ςE-specific anti-ς factor. Here we show that ςE activity is primarily determined by the ratio of RseA to ςE. RseA is rapidly degraded in response to extracytoplasmic stress, leading to an increase in the free pool of ςE and initiation of the stress response. We present evidence that the putative inner membrane serine protease, DegS, is responsible for this regulated degradation of RseA.