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Catalytic domain of the Serine/Threonine Kinase, Mixed Lineage Kinase 2 STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. MLK2 is a mitogen-activated protein kinase kinase kinase (MAP3K, MKKK, MAPKKK) and is also called MAP3K10. MAP3Ks phosphorylate and activate MAPK kinases (MAPKKs or MKKs or MAP2Ks), which in turn phosphorylate and activate MAPKs during signaling cascades that are important in mediating cellular responses to extracellular signals. MLK2 is abundant in brain, skeletal muscle, and testis. It functions upstream of the MAPK, c-Jun N-terminal kinase. It binds hippocalcin, a calcium-sensor protein that protects neurons against calcium-induced cell death. Both MLK2 and hippocalcin may be associated with the pathogenesis of Parkinson's disease. MLK2 also binds to normal huntingtin (Htt), which is important in neuronal transcription, development, and survival. MLK2 does not bind to the polyglutamine-expanded Htt, which is implicated in the pathogeneis of Huntington's disease, leading to neuronal toxicity. Mammals have four MLKs, mostly conserved in vertebrates, which contain an SH3 domain, a catalytic kinase domain, a leucine zipper, a proline-rich region, and a CRIB domain that mediates binding to GTP-bound Cdc42 and Rac. MLKs play roles in immunity and inflammation, as well as in cell death, proliferation, and cell cycle regulation. The MLK2 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 (PI3K). |
Jiyao W et al.(2023). "The conserved domain database in 2023.",