Catalytic domain of the Serine/Threonine kinase, eukaryotic translation Initiation Factor 2-Alpha Kinase 2 or Heme-Regulated Inhibitor kinase
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. HRI (or EIF2AK1) contains an N-terminal regulatory heme-binding domain and a C-terminal catalytic kinase domain. It is suppressed under normal conditions by binding of the heme iron, and is activated during heme deficiency. It functions as a critical regulator that ensures balanced synthesis of globins and heme, in order to form stable hemoglobin during erythroid differentiation and maturation. HRI also protects cells and enhances survival under iron-deficient conditions. EIF2AKs phosphorylate the alpha subunit of eIF-2, resulting in the downregulation of protein synthesis. The HRI 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.
Jiyao W et al.(2023). "The conserved domain database in 2023.",