Protecting from Envelope Stress: Variations on the Phage-Shock-Protein Theme

Abstract

During envelope stress, critical inner-membrane functions are preserved by the phage-shockprotein (Psp) system, a stress response that emerged from work with Escherichia coli and other Gram-negative bacteria. Reciprocal regulatory interactions and multiple effector functions are well documented in these organisms. Searches for the Psp system across phyla reveals conservation of only one protein, PspA. However, examination of Firmicutes and Actinobacteria reveals that PspA orthologs associate with non-orthologous regulatory and effector proteins retaining functions similar to those in Gram-negative counterparts. Conservation across phyla emphasizes the longstanding importance of the Psp system in prokaryotes, while inter-and intra-phyla variations within the system indicate adaptation to different cell envelope structures, bacterial lifestyles, and/or bacterial morphogenetic strategies.

Adaptation to host in Vibrio vulnificus, a zoonotic pathogen that causes septicemia in fish and humans

“…We obtained strong evidences of cell damage and stress response in eel serum, because multiple genes related to membrane regeneration were highly upregulated as well as genes for different stress‐related protective proteins (Mathur and Waldor, ; Mathur et al ., ; Phadtare and Severinov, ; Manganelli and Gennaro, ) (Table and Supporting Information Table S2). Remarkably, the R99 strain seemed to respond specifically against oxidative/nitrosative stress by downregulating genes for two repressors, ohr and nsr , and upregulating an activator, norR , together with genes for various hydroperoxidases, a glutathione synthetase and a hydroxylamine reductase (Fuangthong et al ., ; Rodionov et al ., ) (Table and Supporting Information Table S2).…”

“…). In addition, the upregulation of arcA in eel serum [linked to the upregulation of pspABC (Manganelli and Gennaro, )], as well as the upregulation of qseB in iron‐overloaded human serum, could also contribute to anaerobic metabolism activation. Indeed, QseB has been described as an activator of anaerobic metabolism in iron‐overloaded media in response to catecolamines (Weigel et al ., ) as well as an activator of motility (Weigel and Demuth, ), a phenotype that is induced in iron‐overloaded human serum (Table and Supporting Information Fig.…”

What is Vipp1 good for?

“…Thus, the homologous PspA, LiaH and Vipp1/IM30 proteins all appear to exhibit their function in large, membrane‐bound clusters, and formation of such membrane‐attached structures appears to be involved in membrane protection under membrane‐stress conditions. This activity likely is conserved in the homologous bacterial proteins and clearly does not involve biogenesis of photosynthetic complexes (Manganelli and Gennaro, ). A membrane‐protective function is also completely in line with the observation that the Vipp1/IM30 protein of the cyanobacterium Synechocystis and of the plant Arabidopsis thaliana can functionally complement the E. coli PspA protein (DeLisa et al ., ; Zhang et al ., ) and that Vipp1/IM30 not only binds to TMs but also to the chloroplast inner envelope membrane (Li et al ., ) and the cyanobacterial cytoplasmic membrane (Srivastava et al ., ; Fuhrmann et al ., ).…”