Janus kinase 2 (commonly called JAK2) is a non-receptor tyrosine kinase. It is a member of the Janus kinase family and has been implicated in signaling by members of the type II cytokine receptor family (e.g. interferon receptors), the GM-CSF receptor family (IL-3R, IL-5R and GM-CSF-R), the gp130 receptor family (e.g., IL-6R), and the single chain receptors (e.g. Epo-R, Tpo-R, GH-R, PRL-R).[5][6]
The distinguishing feature between janus kinase 2 and other JAK kinases is the lack of Src homology binding domains (SH2/SH3) and the presence of up to seven JAK homology domains (JH1-JH7). Nonetheless the terminal JH domains retain a high level of homology to tyrosine kinase domains. An interesting note is that only one of these carboxy-terminal JH domains retains full kinase function (JH1) while the other (JH2), previously thought to have no kinase functionality and accordingly termed a pseudokinase domain, has since been found to be catalytically active, albeit at only 10% that of the JH1 domain.[7][8]
Loss of JAK2 is lethal by embryonic day 12 in mice.[9]
JAK2 orthologs[10] have been identified in all mammals for which complete genome data are available.
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- ^ Ungureanu D, Wu J, Pekkala T, Niranjan Y, Young C, Jensen ON, Xu CF, Neubert TA, Skoda RC, Hubbard SR, Silvennoinen O (August 2011). "The pseudokinase domain of JAK2 is a dual-specificity protein kinase that negatively regulates cytokine signaling". Nature Structural & Molecular Biology. 18 (9): 971–976. doi:10.1038/nsmb.2099. PMC 4504201. PMID 21841788.
- ^ Neubauer H, Cumano A, Müller M, Wu H, Huffstadt U, Pfeffer K (May 1998). "Jak2 deficiency defines an essential developmental checkpoint in definitive hematopoiesis". Cell. 93 (3): 397–409. doi:10.1016/S0092-8674(00)81168-X. PMID 9590174. S2CID 11375232.
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