Activity of a Bacterial Cell Envelope Stress Response is Controlled by the Interaction of a Protein-binding Domain with Different Partners [Gene Regulation]

March 23rd, 2015 by Flores-Kim, J., Darwin, A. J.

The bacterial phage shock protein (Psp) system is a highly conserved cell envelope stress response required for virulence in Yersinia enterocolitica and Salmonella enterica. In non-inducing conditions the transcription factor PspF is inhibited by an interaction with PspA. In contrast, PspA associates with the cytoplasmic membrane proteins PspBC during inducing conditions. This has led to the proposal that PspBC exist in an OFF state, which cannot recruit PspA, or an ON state, which can. However, nothing was known about the difference between these two states. Here, we provide evidence that it is the C-terminal domain of Y. enterocolitica PspC (PspCCT) that interacts directly with PspA, both in vivo and in vitro. Site-specific photo-cross-linking revealed that this interaction occurred only during Psp inducing conditions in vivo. Importantly, we have also discovered that PspCCT can interact with the C-terminal domain of PspB (PspCCT-PspBCT). However, the PspCCT-PspBCT and PspCCT-PspA interactions were mutually exclusive in vitro. Furthermore, in vivo, PspCCT contacted PspBCT in the OFF state, whereas it contacted PspA in the ON state. These findings provide the first description of the previously proposed PspBC OFF and ON states and reveal that the regulatory switch is centered on a PspCCT partner-switching mechanism.
  • Posted in Journal of Biological Chemistry, Publications
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