THE RESPONSE REGULATOR SPRE CONTROLS THE STABILITY OF RPOS

In Escherichia coli, the sigma factor, RpoS, is a central regulator in stationary-phase cells. We have identified a gene, sprE (stationary-p hase regulator), as essential for the negative regulation of rpoS expr ession. SprE negatively regulates the rpoS gene product at the level o f protein stability, perhaps in response to nutrient availability. The ability of SprE to destabilize RpoS is dependent on the ClpX/ClpP pro tease. Based on homology, SprE is a member of the response regulator f amily of proteins. SprE is the first response regulator identified tha t is implicated in the control of protein stability. Moreover, SprE is the first reported protein that appears to regulate rpoS in response to a specific environmental parameter.