The Y ersinia pseudotuberculosis degradosome is required for oxidative stress, while its PNP ase subunit plays a degradosome‐independent role in cold growth

Yersinia polynucleotide phosphorylase ( PNP ase), a 3′–5′ exoribonuclease, has been shown to affect growth during several stress responses. In E scherichia coli , PNP ase is one of the subunits of a multiprotein complex known as the degradosome, but also has degradosome‐independent functions. The carboxy‐terminus of E . coli ribonuclease E ( RN ase E ) serves as the scaffold upon which PNP ase, enolase (a glycolytic enzyme), and R hl B helicase all have been shown to bind. In the yersiniae, only PNP ase has thus far been shown to physically interact with RN ase E . We show by bacterial two‐hybrid and co‐immunoprecipitation assays that R hl B and enolase also interact with RN ase E . Interestingly, although PNP ase is required for normal growth at cold temperatures, assembly of the yersiniae degradosome was not required. However, degradosome assembly was required for growth in the presence of reactive oxygen species. These data suggest that while the Y ersinia pseudotuberculosis PNP ase plays a role in the oxidative stress response through a degradosome‐dependent mechanism, PNP ase's role during cold stress is degradosome‐independent.