查看文章

The alternative sigma factor σ^E is activated in response to stress in the extracytoplasmic compartment of Escherichia coli. Here we show that σ^E activity increases upon initiation of the stress response by a shift to an elevated temperature (43°C) and remains at that level for the duration of the stress. When the stress is removed by a temperature downshift, σ^E activity is strongly repressed and then slowly returns to levels seen in unstressed cells. We provide evidence that information about the state of the cell envelope is communicated to σ^E primarily through the regulated proteolysis of the inner membrane anti-sigma factor RseA, as the degradation rate of RseA is correlated with the changes in σ^E activity throughout the stress response. However, the relationship between σ^E activity and the rate of degradation of RseA is complex, indicating that other factors may cooperate with RseA and serve to fine-tune the response.