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Catalytic domain of the Serine/Threonine Kinase, SNF1-related kinase STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. SNRK is a kinase highly expressed in testis and brain that is found inactive in cells that lack the LKB1 tumour suppressor protein kinase. The regulatory subunits STRAD and MO25 are required for LKB1 to activate SNRK. The SNRK mRNA is increased 3-fold when granule neurons are cultured in low potassium, and may thus play a role in the survival responses in these cells. In some vertebrates, a second SNRK gene (snrkb or snrk-1) has been sequenced and/or identified. Snrk-1 is expressed specifically in embryonic zebrafish vasculature; it plays an essential role in angioblast differentiation, maintenance, and migration. The SNRK 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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