The Phage-shock-protein (PSP) Envelope Stress Response: Discovery of Novel Partners and Evolutionary History

Abstract

AbstractThe phage shock protein (PSP) systems orchestrate a conserved stress response function by stabilizing the cell membrane and protecting bacteria from envelope stress. The full repertoire of PSP components remains poorly characterized. We combined comparative genomics and protein sequence-structure-function analyses to systematically identify homologs, phyletic patterns, domain architectures, and gene neighborhoods to trace the evolution of PSP components across the tree of life. This approach showed that the core component PspA/Snf7 (Psp/ESCRT systems) was present in the Last Universal Common Ancestor and that different clades co-opted a diverse range of partners to constitute distinct PSP systems. We identified several novel partners of the PSP system: (i) the Toastrack domain, which likely facilitates assembling diverse sub-membrane stress-sensing and signaling complexes, (ii) the newly-defined HAAS–PadR-like transcription regulator pair system, and (iii) multiple independent associations with ATPase or CesT/Tir-like chaperones, and Band-7 domain proteins that likely mediate sub-membrane dynamics. Our work also uncovered links between the PSP components and diverse SHOCT-like domains, suggesting a role in assembling membrane-associated complexes of proteins with disparate biochemical functions. Tracing the evolution of Psp cognate proteins provides new insights into the functions of the system and helps predict previously uncharacterized, often lineage-specific, membrane-dynamics and stress-response systems. The conservation of PSP systems across bacterial phyla emphasizes the importance of this stress response system in prokaryotes, while its modular diversity in various lineages indicates the emergence of lineage-specific cell-envelope structures, lifestyles, and adaptation mechanisms. The results can be accessed at https://jravilab.shinyapps.io/psp-evolution.