Catalytic domain of the Serine/Threonine kinase, eukaryotic translation Initiation Factor 2-Alpha Kinase
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. EIF2AKs phosphorylate 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 under different stress conditions: General Control Non-derepressible-2 (GCN2) which is activated during amino acid or serum starvation; protein kinase regulated by RNA (PKR) which is activated by double stranded RNA; heme-regulated inhibitor kinase (HRI) which is activated under heme-deficient conditions; and PKR-like endoplasmic reticulum kinase (PERK) which is activated when misfolded proteins accumulate in the ER. The EIF2AK subfamily is part of a larger superfamily that includes the catalytic domains of other protein STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.
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