The Luminal domain, a dimerization domain, of the Serine/Threonine protein kinase, eukaryotic translation Initiation Factor 2-Alpha Kinase 3
The Luminal domain is a dimerization domain present in eukaryotic translation Initiation Factor 2-Alpha Kinase 3 (EIF2AK3), also called PKR-like Endoplasmic Reticulum Kinase (PERK). EIF2AK3 is a serine/threonine protein kinase (STK) and a type I transmembrane protein that is localized in the endoplasmic reticulum (ER). As a EIF2AK, it phosphorylates the alpha subunit of eIF-2, resulting in the downregulation of protein synthesis. eIF-2 phosphorylation is induced in response to cellular stresses including virus infection, heat shock, nutrient deficiency, and the accummulation of unfolded proteins, among others. There are four distinct kinases that phosphorylate eIF-2 and control protein synthesis: General Control Non-derepressible-2 (GCN2), protein kinase regulated by RNA (PKR), heme-regulated inhibitor kinase (HRI), and PERK. PERK contains a luminal domain bound with the chaperone BiP under unstressed conditions and a cytoplasmic catalytic kinase domain. In response to the accumulation of misfolded or unfolded proteins in the ER, PERK is activated through the release of BiP, allowing it to dimerize through its luminal domain and autophosphorylate. It functions as the central regulator of translational control during the Unfolded Protein Response (UPR) pathway. In addition to the eIF-2 alpha subunit, PERK also phosphorylates Nrf2, a leucine zipper transcription factor which regulates cellular redox status and promotes cell survival during the UPR.
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