Journal Article A Novel SRP Recognition Sequence in the Homeostatic Control Region of Heat Shock Transcription Factor σ[32].

Miyazaki, Ryoji  ,  Yura, Takashi  ,  Suzuki, Takehiro  ,  Dohmae, Naoshi  ,  Mori, Hiroyuki  ,  Akiyama, Yoshinori

62016-04-07 , Nature Publishing Group
Heat shock response (HSR) generally plays a major role in sustaining protein homeostasis. In Escherichia coli, the activity and amount of the dedicated transcription factor σ[32] transiently increase upon heat shock. The initial induction is followed by chaperone-mediated negative feedback to inactivate and degrade σ[32]. Previous work reported that signal recognition particle (SRP)-dependent targeting of σ[32] to the membrane is essential for feedback control, though how SRP recognizes σ[32] remained unknown. Extensive photo- and disulfide cross-linking studies in vivo now reveal that the highly conserved regulatory region of σ[32] that lacks a consecutive hydrophobic stretch interacts with the signal peptide-binding site of Ffh (the protein subunit of SRP). Importantly, the σ[32]–Ffh interaction observed was significantly affected by mutations in this region that compromise the feedback regulation, but not by deleting the DnaK/DnaJ chaperones. Homeostatic regulation of HSR thus requires a novel type of SRP recognition mechanism.

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