Catalytic domain of the Serine/Threonine Kinase, Mitogen-Activated Protein Kinase 15 and similar MAPKs
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. Human MAPK15 is also called Extracellular signal Regulated Kinase 8 (ERK8) while the rat protein is called ERK7. ERK7 and ERK8 display both similar and different biochemical properties. They autophosphorylate and activate themselves and do not require upstream activating kinases. ERK7 is constitutively active and is not affected by extracellular stimuli whereas ERK8 shows low basal activity and is activated by DNA-damaging agents. ERK7 and ERK8 also have different substrate profiles. Genome analysis shows that they are orthologs with similar gene structures. ERK7 and ERK 8 may be involved in the signaling of some nuclear receptor transcription factors. ERK7 regulates hormone-dependent degradation of estrogen receptor alpha while ERK8 down-regulates the transcriptional co-activation androgen and glucocorticoid receptors. MAPKs are important mediators of cellular responses to extracellular signals. The MAPK15 subfamily is part of a larger superfamily that includes the catalytic domains of other STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.
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