THE CPX 2-COMPONENT SIGNAL-TRANSDUCTION PATHWAY OF ESCHERICHIA-COLI REGULATES TRANSCRIPTION OF THE GENE SPECIFYING THE STRESS-INDUCIBLE PERIPLASMIC PROTEASE, DEGP

DegP is a heat-shock inducible periplasmic protease in Escherichia col i. Unlike the cytoplasmic heat shock proteins, DegP is not transcripti onally regulated by the classical heat shock regulon coordinated by si gma(32) Rather, the degP gene is transcriptionally regulated by an alt ernate heat shock sigma factor, sigma(E). Previous studies have demons trated a signal transduction pathway that monitors the amount of outer -membrane proteins in the bacterial envelope and modulates degP levels in response to this extracytoplasmic parameter. To analyze the transc riptional regulation of degP, we examined mutations that altered trans cription of a degP-lacZ operon fusion. Gain-of-function mutations in c pxA, which specifies a two-component sensor protein, stimulate transcr iption from degP. Defined null mutations in cpxA or the gene encoding its cognate response regulator, cpxR, decrease transcription from degP . These null mutations also prevent transcriptional induction of degP in response to overexpression of a gene specifying an envelope lipopro tein. Cpx-mediated transcription of degP is partially dependent on the activity of E sigma(E), suggesting that the Cpx pathway functions in concert with E sigma(E) and perhaps other RNA polymerases to drive tra nscription of degP.