Regulation of the Phage-Shock-Protein Stress Response in Yersinia enterocolitica

The phage-shock-protein (Psp) system of Yersinia enterocolitica encodes a stress response that is essential for viability when the secretin component of its Ysc type III secretion system is produced. Therefore, Y. enterocolitica psp null mutants are completely avirulent in a mouse model of infection. This article summarizes what is known about the regulation of the Y. enterocolitica Psp system. psp gene expression is induced by the overproduction of secretins, some cytoplasmic membrane proteins, or disruption of the F0F1-ATPase. All of these may deplete the proton-motive force, which could be the inducing signal for the Psp system. None of these Psp triggers induce two other extracytoplasmic stress responses (RpoE and Cpx), which suggests that the inducing signal of the Psp system is specific. The induction of psp gene expression requires the cytoplasmic membrane proteins PspB and PspC, which interact and presumably work together to achieve their regulatory function. However, the regulatory role of PspBC does not completely explain why they are essential for survival during secretin-stress, suggesting that they have a second unrelated role. Finally, current ideas about how PspB/C might sense the inducing trigger(s) are briefly discussed, including a consideration of whether there might be any unidentified signal transduction components that communicate with the Psp system.