degS ( hhoB ) is an essential Escherichia coli gene whose indispensable function is to provide σ E activity

DegS (HhoB), a putative serine protease related to DegP/HtrA, regulates the basal and induced activity of the essential Escherichia coli sigma factor σ E , which is involved in the cellular response to extracytoplasmic stress. DegS promotes the destabilization of the σ E ‐specific anti‐sigma factor RseA, thereby releasing σ E to direct gene expression. We demonstrate that degS is an essential E. coli gene and show that the essential function of DegS is to provide the cell with σ E activity. We also show that the putative active site of DegS is periplasmic and that DegS requires its N‐terminal transmembrane domain for its σ E ‐related function.