Perk, or Protein Kinase R (PKR)-like ER kinase, is an enzyme that plays a critical role in the unfolded protein response (UPR) within the endoplasmic reticulum (ER). The UPR is a cellular stress response related to the ER's function. Perk helps to reduce the load of unfolded proteins by phosphorylating the eukaryotic initiation factor 2α (eIF2α), which reduces general protein synthesis but selectively increases the translation of specific proteins that aid in stress adaptation.
