Client protein-driven reversal of endoplasmic reticulum chaperone (BiP) mediated-repression is revealed as a principal component of the regulation of the unfolded protein response transducer IRE1 in cells.
Quantitative FRET UPR induction assay is used to measure IRE1 and BIP association and dissociation by a variety of ER misfolded proteins and by an important BiP substrate-binding domain mutant, significantly enhancing the evidence for the allosteric UPR induction model.
The molecular chaperone BIP from the endoplasmic reticulum is fine-tuned postranslationally through the thermodynamic and kinetic alterations in its conformational ensemble of functionally and structurally distinct physiological forms.
The extent of (proteotoxic) endoplasmic reticulum stress, and the ensuing unfolded protein response activation, are commensurate with the extent of the chaperone BiP being sequestered by its client proteins.
SAK1, a novel cytoplasmic phosphoprotein, is a key intermediate component of the retrograde signaling pathway controlling nuclear gene expression during acclimation of Chlamydomonas cells to singlet oxygen stress.
Direct modification by endogenous peroxide of a conserved cysteine in the molecular chaperone BiP decouples its ATPase and peptide-binding activities, allowing for enhanced polypeptide holdase activity during oxidative stress.