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.