Q9Z2R9 (E2AK1_MOUSE) Reviewed, UniProtKB/Swiss-Prot
Last modified November 13, 2013. Version 123. History...
Names and origin
|Protein names||Recommended name:|
Eukaryotic translation initiation factor 2-alpha kinase 1
Heme-regulated eukaryotic initiation factor eIF-2-alpha kinase
Hemin-sensitive initiation factor 2-alpha kinase
|Organism||Mus musculus (Mouse) [Reference proteome]|
|Taxonomic identifier||10090 [NCBI]|
|Taxonomic lineage||Eukaryota › Metazoa › Chordata › Craniata › Vertebrata › Euteleostomi › Mammalia › Eutheria › Euarchontoglires › Glires › Rodentia › Sciurognathi › Muroidea › Muridae › Murinae › Mus › Mus|
|Sequence length||619 AA.|
|Protein existence||Evidence at protein level|
General annotation (Comments)
Inhibits protein synthesis at the translation initiation level, in response to various stress conditions, including oxidative stress, heme deficiency, osmotic shock and heat shock. Exerts its function through the phosphorylation of EIF2S1 at 'Ser-48' and 'Ser-51', thus preventing its recycling. Binds hemin forming a 1:1 complex through a cysteine thiolate and histidine nitrogenous coordination. This binding occurs with moderate affinity, allowing it to sense the heme concentration within the cell. Thanks to this unique heme-sensing capacity, plays a crucial role to shut off protein synthesis during acute heme-deficient conditions. In red blood cells (RBCs), controls hemoglobin synthesis ensuring a coordinated regulation of the synthesis of its heme and globin moieties. Thus plays an essential protective role for RBC survival in anemias of iron deficiency. Similarly, in hepatocytes, involved in heme-mediated translational control of CYP2B and CYP3A and possibly other hepatic P450 cytochromes. May also contain ER stress during acute heme-deficient conditions. Ref.2 Ref.10 Ref.12
ATP + a protein = ADP + a phosphoprotein.
Induced by acute heme depletion, that not only increases EIF2AK1 protein levels, but also stimulates kinase activity by autophosphorylation. Inhibited by the heme-degradation products biliverdin and bilirubin. Induced by oxidative stress generated by arsenite treatment. Binding of nitric oxide (NO) to the heme iron in the N-terminal heme-binding domain activates the kinase activity, while binding of carbon monoxide (CO) suppresses kinase activity. Ref.8 Ref.9 Ref.12
Synthesized in an inactive form that binds to the N-terminal domain of CDC37. Has to be associated with a multiprotein complex containing Hsp90, CDC37 and PPP5C for maturation and activation by autophosphorylation. The phosphatase PPP5C modulates this activation By similarity. Forms oligomers. Has been reported as a homodimer, as well as a hexamer in the absence of hemin. Converted to an inactive disulfide linked homodimer in the presence of hemin. Ref.10
Expressed predominantly in erythroid cells, mature reticulocytes, as well as fetal liver nucleated erythroid cells. At much lower levels, expressed in hepatocytes and bone marrow-derived macrophages (at protein level). Ref.7 Ref.11 Ref.12
Highly expressed in fetal liver erythroid precursor cells at 14.5 dpc (at protein level). Ref.11
Activated by autophosphorylation; phosphorylated predominantly on serine and threonine residues, but also on tyrosine residues. Autophosphorylation at Thr-485 is required for kinase activation. The active autophosphorylated form apparently is largely refractory to cellular heme fluctuations. Ref.1 Ref.6 Ref.8
|Involvement in disease|
Defects in Eif2ak1 are a cause of hyperchromic anemia in animals suffering from iron deficiency. The number of red blood cells is decreased due to increased apoptosis of erythroid precursor cells, probably because globins misfold and aggregate in the absence of heme.
Mice are viable and fertile without gross morphological abnormalities. Dramatically altered response to diet-induced iron deficiency shifting from an adaptive decrease in RBC volume and intracellular hemoglobin content to an increased production of abnormally dense red blood cells (RBCs) with decreasing red cell counts. The decrease in RBC number is the result of increased apoptosis of erythroid precursors. Diminished levels of phosphorylated EIF2S1 in bone marrow-derived macrophages (BMDMs). Impaired maturation of BMDMs and blunted inflammatory response to LPS with a reduced cytokine production. Impaired phagocytosis of senescent RBCs by macrophages, resulting in a lower phagocytosis index and lower percentage of macrophages with ingested RBC. In hepatocytes, cytochromes P450 CYP2B6 and CYP3A induction by phenobarbital is not impaired in response to acute heme depletion and CYP2B6 and CYP3A proteins continue to accumulate to supranormal levels, irrespective of the hepatic heme pool status. These cells also exhibit a weak, albeit significant, elevation of the basal ER-stress as reflected by elevated levels of autophosphorylated EIF2AK3/PERK and EIF2AK4/GCN2, the ER-stress related chaperones HSPA5 and HSP90B1, and total hepatic protein ubiquitination. Ref.2 Ref.11 Ref.12
Contains 2 HRM (heme regulatory motif) repeats.
Contains 1 protein kinase domain.
The sequence BAD32438.1 differs from that shown. Reason: Erroneous initiation. Translation N-terminally shortened.
Sequence annotation (Features)
|Feature key||Position(s)||Length||Description||Graphical view||Feature identifier|
|Chain||1 – 619||619||Eukaryotic translation initiation factor 2-alpha kinase 1||PRO_0000085942|
|Domain||167 – 580||414||Protein kinase|
|Repeat||408 – 413||6||HRM 1|
|Repeat||549 – 554||6||HRM 2|
|Nucleotide binding||173 – 181||9||ATP By similarity|
|Active site||440||1||Proton acceptor By similarity|
|Binding site||196||1||ATP By similarity|
|Site||80||1||Heme-binding By similarity|
Amino acid modifications
|Modified residue||483||1||Phosphothreonine; by autocatalysis Ref.8|
|Modified residue||485||1||Phosphothreonine; by autocatalysis Ref.8|
|Mutagenesis||196||1||K → R: Abolishes kinase activity. Ref.1 Ref.8|
|Mutagenesis||483||1||T → A: No effect on kinase activity. Ref.8|
|Mutagenesis||483||1||T → D: No effect on kinase activity. Ref.8|
|Mutagenesis||485||1||T → A: Abolishes kinase activity. Ref.8|
|Mutagenesis||485||1||T → D: Constitutively active kinase; loss of regulation by heme and arsenite. Ref.8|
|Mutagenesis||490||1||T → A: Almost complete loss of kinase activity; even upon arsenite treatment. Ref.8|
|Mutagenesis||490||1||T → D: Almost complete loss of kinase activity; even upon arsenite treatment. Ref.8|
|Sequence conflict||20||1||A → S in BAB32242. Ref.5|
|Sequence conflict||71||1||S → C in BAB32242. Ref.5|
|Sequence conflict||138 – 150||13||DPCQD…MQKIR → VSPTGCTLYDKYI in BAB32242. Ref.5|
|Sequence conflict||196 – 197||2||KK → IE in BAB29545. Ref.5|
|Sequence conflict||371||1||E → D in AAC79201. Ref.1|
|Sequence conflict||371||1||E → D in AAK55766. Ref.2|
|Sequence conflict||565||1||V → A in AAH28923. Ref.4|
|||"Characterization of the hemin-sensitive eukaryotic initiation factor 2alpha kinase from mouse nonerythroid cells."|
Berlanga J.J., Herrero S., de Haro C.
J. Biol. Chem. 273:32340-32346(1998) [PubMed] [Europe PMC] [Abstract]
Cited for: NUCLEOTIDE SEQUENCE [MRNA], MUTAGENESIS OF LYS-196, AUTOPHOSPHORYLATION.
Strain: C57BL/6 X CBA.
|||"Heme-regulated eIF2alpha kinase (HRI) is required for translational regulation and survival of erythroid precursors in iron deficiency."|
Han A.-P., Yu C., Lu L., Fujiwara Y., Browne C., Chin G., Fleming M., Leboulch P., Orkin S.H., Chen J.-J.
EMBO J. 20:6909-6918(2001) [PubMed] [Europe PMC] [Abstract]
Cited for: NUCLEOTIDE SEQUENCE [MRNA], FUNCTION, DISRUPTION PHENOTYPE.
|||"Prediction of the coding sequences of mouse homologues of KIAA gene: IV. The complete nucleotide sequences of 500 mouse KIAA-homologous cDNAs identified by screening of terminal sequences of cDNA clones randomly sampled from size-fractionated libraries."|
Okazaki N., Kikuno R., Ohara R., Inamoto S., Koseki H., Hiraoka S., Saga Y., Seino S., Nishimura M., Kaisho T., Hoshino K., Kitamura H., Nagase T., Ohara O., Koga H.
DNA Res. 11:205-218(2004) [PubMed] [Europe PMC] [Abstract]
Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE MRNA].
Tissue: Pancreatic islet.
|||"The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC)."|
The MGC Project Team
Genome Res. 14:2121-2127(2004) [PubMed] [Europe PMC] [Abstract]
Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE MRNA].
Strain: C57BL/6J and FVB/N.
Tissue: Eye and Salivary gland.
|||"The transcriptional landscape of the mammalian genome."|
Carninci P., Kasukawa T., Katayama S., Gough J., Frith M.C., Maeda N., Oyama R., Ravasi T., Lenhard B., Wells C., Kodzius R., Shimokawa K., Bajic V.B., Brenner S.E., Batalov S., Forrest A.R., Zavolan M., Davis M.J. Hayashizaki Y.
Science 309:1559-1563(2005) [PubMed] [Europe PMC] [Abstract]
Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE MRNA] OF 1-211 AND 445-619.
Tissue: Head, Olfactory bulb and Retina.
|||"Multiple autophosphorylation is essential for the formation of the active and stable homodimer of heme-regulated eIF2alpha kinase."|
Bauer B.N., Rafie-Kolpin M., Lu L., Han A., Chen J.-J.
Biochemistry 40:11543-11551(2001) [PubMed] [Europe PMC] [Abstract]
Cited for: AUTOPHOSPHORYLATION ON SERINE; THREONINE AND TYROSINE RESIDUES, HEME-BINDING.
|||"Translation initiation control by heme-regulated eukaryotic initiation factor 2alpha kinase in erythroid cells under cytoplasmic stresses."|
Lu L., Han A.P., Chen J.J.
Mol. Cell. Biol. 21:7971-7980(2001) [PubMed] [Europe PMC] [Abstract]
Cited for: REGULATION BY HEME DEFICIENCY; HEAT SHOCK; OSMOTIC STRESS AND OXIDATIVE STRESS, TISSUE SPECIFICITY.
|||"Autophosphorylation of threonine 485 in the activation loop is essential for attaining eIF2alpha kinase activity of HRI."|
Rafie-Kolpin M., Han A.P., Chen J.J.
Biochemistry 42:6536-6544(2003) [PubMed] [Europe PMC] [Abstract]
Cited for: AUTOPHOSPHORYLATION AT THR-483; THR-485 AND THR-490, ENZYME REGULATION, MUTAGENESIS OF LYS-196; THR-483; THR-485 AND THR-490.
|||"Activation of heme-regulated eukaryotic initiation factor 2alpha kinase by nitric oxide is induced by the formation of a five-coordinate NO-heme complex: optical absorption, electron spin resonance, and resonance raman spectral studies."|
Igarashi J., Sato A., Kitagawa T., Yoshimura T., Yamauchi S., Sagami I., Shimizu T.
J. Biol. Chem. 279:15752-15762(2004) [PubMed] [Europe PMC] [Abstract]
Cited for: HEME-BINDING, ENZYME REGULATION.
|||"Characterization of heme-regulated eIF2alpha kinase: roles of the N-terminal domain in the oligomeric state, heme binding, catalysis, and inhibition."|
Miksanova M., Igarashi J., Minami M., Sagami I., Yamauchi S., Kurokawa H., Shimizu T.
Biochemistry 45:9894-9905(2006) [PubMed] [Europe PMC] [Abstract]
Cited for: FUNCTION, OLIGOMERIZATION, HEME-BINDING, INDUCTION.
|||"The function of heme-regulated eIF2alpha kinase in murine iron homeostasis and macrophage maturation."|
Liu S., Suragani R.N., Wang F., Han A., Zhao W., Andrews N.C., Chen J.J.
J. Clin. Invest. 117:3296-3305(2007) [PubMed] [Europe PMC] [Abstract]
Cited for: SUBCELLULAR LOCATION, TISSUE SPECIFICITY, DEVELOPMENTAL STAGE, DISRUPTION PHENOTYPE.
|||"Hepatic heme-regulated inhibitor (HRI) eukaryotic initiation factor 2alpha kinase: a protagonist of heme-mediated translational control of CYP2B enzymes and a modulator of basal endoplasmic reticulum stress tone."|
Acharya P., Chen J.J., Correia M.A.
Mol. Pharmacol. 77:575-592(2010) [PubMed] [Europe PMC] [Abstract]
Cited for: FUNCTION, TISSUE SPECIFICITY, ENZYME REGULATION, DISRUPTION PHENOTYPE.
|+||Additional computationally mapped references.|
|AF028808 mRNA. Translation: AAC79201.1.|
AY033898 mRNA. Translation: AAK55766.1.
AK173160 mRNA. Translation: BAD32438.1. Different initiation.
BC028923 mRNA. Translation: AAH28923.1.
BC111035 mRNA. Translation: AAI11036.1.
AK014775 mRNA. Translation: BAB29545.1.
AK020887 mRNA. Translation: BAB32242.1.
AK032508 mRNA. Translation: BAC27901.1.
|RefSeq||NP_038585.2. NM_013557.2. |
3D structure databases
|SMR||Q9Z2R9. Positions 162-235, 378-619. |
Protein-protein interaction databases
|IntAct||Q9Z2R9. 2 interactions.|
Protocols and materials databases
Genome annotation databases
|Ensembl||ENSMUST00000100487; ENSMUSP00000098056; ENSMUSG00000029613. |
|UCSC||uc029vqe.1. mouse. |
|MGI||MGI:1353448. Eif2ak1. |
Gene expression databases
Family and domain databases
|InterPro||IPR011009. Kinase-like_dom. |
|Pfam||PF00069. Pkinase. 2 hits. |
|SUPFAM||SSF56112. SSF56112. 2 hits. |
|PROSITE||PS00107. PROTEIN_KINASE_ATP. 1 hit. |
PS50011. PROTEIN_KINASE_DOM. 1 hit.
PS00108. PROTEIN_KINASE_ST. 1 hit.
|ChiTaRS||EIF2AK1. mouse. |
|Accession||Primary (citable) accession number: Q9Z2R9|
Secondary accession number(s): Q2TA96 Q9D601
|Entry status||Reviewed (UniProtKB/Swiss-Prot)|
|Annotation program||Chordata Protein Annotation Program|