Phage shock protein, a stress protein of Escherichia coli.

Abstract

Filamentous phage infection induces the synthesis of large amounts of an Escherichia coli protein, phage shock protein (Psp), the product of a previously undescribed gene. This induction is due to the phage gene IV protein, pIV, an integral membrane protein. The uninduced level of Psp is undetectable, but when induced by prolonged synthesis of pIV, it can become one of the most abundant proteins in the cell. Psp is also synthesized transiently in response to several stresses (heat, ethanol, and osmotic shock). High-level synthesis occurs only after extreme treatment. Unlike the members of the heat shock regulon, Psp induction does not require the heat shock sigma factor, sigma 32; some stimuli that elicit sigma 32-dependent heat shock proteins do not induce Psp synthesis. The level of Psp induction after extreme stress is even higher in sigma 32 mutant cells, which are unable to mount a normal heat shock response, suggesting that these parallel stress responses are interrelated.

The Escherichia coli phage‐shock‐protein (psp) operon

“…PspA is a peripheral membrane protein, approx. 50% of which is associated with the inner membrane fraction from E. coli (Brissette et al, 1990). PspB and C are both inner membrane proteins Kleerebezem et al, 1996), and PspE is periplasmic Mielke and Russel, 1992 Upper part.…”

“…The psp operon was discovered during the course of cloning filamentous-phage gene IV; overexpression of pIV, which is an outer membrane protein, from a runaway plasmid (Brissette et al, 1990) induced such abundant synthesis of PspA protein that it became a major fraction of the total cell protein. The operon contains several open reading frames (ORFs), at least four of which (PspA, B, C, and E) are expressed in vivo and in vitro; the product of the first gene, pspA, is the most abundant .…”

“…PspA expression is induced after filamentous-phage infection, as well as when gene IV is expressed from a plasmid (Brissette et al, 1990;Russel and Kazmierczak, 1993). Transcription of the operon is also induced by expression of pIV homologues from several different bacteria (Possot et al, 1992;Russel and Kazmierczak, 1993) or by overexpression of some outer membrane porins, particularly mutant porins defective in some aspect of integration into the outer membrane (Bosch and Tommassen, 1987;Carlson and Silhavy, 1993;Kleerebezem and Tommassen, 1993).…”

“…Transcription of the operon is also induced by expression of pIV homologues from several different bacteria (Possot et al, 1992;Russel and Kazmierczak, 1993) or by overexpression of some outer membrane porins, particularly mutant porins defective in some aspect of integration into the outer membrane (Bosch and Tommassen, 1987;Carlson and Silhavy, 1993;Kleerebezem and Tommassen, 1993). Stresses, such as extreme heat shock or treatment with 10% ethanol and hyper-(but not hypo-) osmotic shock are also inducers (Brissette et al, 1990), but it is not clear whether these stimuli, many of which are lethal to the cell, elicit a normal induction response or short-circuit the normal controls on psp expression. The psp genes are also induced by media downshifts, and are induced very strongly by proton ionophores such as CCCP or other uncouplers (dinitrophenol or free fatty acids) (Weiner and Model, 1994), and by disruption of fatty acid biosynthesis, either by mutation or with the inhibitors diazaborine or cerulenin (Bergler et al, 1994).…”

“…In addition, PspA protein is a major component of the limited protein synthesis that occurs during late stationary phase (Weiner and Model, 1994). Other than expression of gene IV or infection with filamentous phage, all the inducing stimuli also induce the 32 -dependent heat-shock genes (groE, dnaK, dnaJ, grpE (Lindquist and Craig, 1988;Yura et al, 1993)), but psp-operon transcription does not require 32 and hence none of the other components of the canonical heat-shock response; indeed, shift of a 32ts mutant to the non-permissive temperature intensifies the psp response, and for the stimuli that induce psp transiently, such as heat and exposure to ethanol, this prolongs the response (Brissette et al, 1990;Weiner et al, 1991). A participant in the canonical heatshock response of E. coli is E , which is responsible for transcription of 32 at 50ЊC (Erickson and Gross, 1989) and is itself activated by overproduction of outer membrane proteins (Mecsas et al, 1993).…”