THE ESCHERICHIA-COLI PHAGE-SHOCK-PROTEIN (PSP) OPERON

The phage-shock-protein (psp) operon helps to ensure survival of Esche richia coli in tate stationary phase at alkaline pH, and protects the cell against dissipation of its proton-motive force against challenge. It is strongly induced by filamentous phage pIV and its bacterial hom ologues, and by mutant porins that don't localize properly, as well as by a number of other stresses. Transcription of the operon is depende nt on sigma(54) and a constitutively active, autogenously controlled a ctivator. psp-operon expression is controlled by one negatively and se veral positively acting regulators, none of which is a DNA-binding pro tein. The major product of the operon, PspA, may also serve as a negat ive regulator of an unusual porin, OmpG.