PERK also named as EIF2AK3 or PEK belongs to the protein kinase superfamily Ser/Thr protein kinase family and GCN2 subfamily.It acts as a metabolic-stress sensing protein kinase that phosphorylates the alpha subunit of eukaryotic translation initiation factor 2 (EIF2S1/eIF-2-alpha) in response to various stress conditions.PERK and EIF2AK4 also have a functional role on regulating translation under non-stressed conditions apart from their long established roles as stress kinases (PMID: 21638082).Defects in EIF2AK3 are the cause of Wolcott-Rallison syndrome (WRS).The molecular mass of PERK is 125 kDa and can be detected as 140 kDa or 170kDa due to some modifications such as glycosylation and phosphorylation (PMID: 20851775 24371088 21703327).