Catalytic domain of the Serine/Threonine protein kinases, Casein Kinase 1 alpha
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. CK1 phosphorylates a variety of substrates including enzymes, transcription and splice factors, cytoskeletal proteins, viral oncogenes, receptors, and membrane-associated proteins. There are mutliple isoforms of CK1 and in mammals, seven isoforms (alpha, beta, gamma1-3, delta, and epsilon) have been characterized. These isoforms differ mainly in the length and structure of their C-terminal non-catalytic region. CK1alpha plays a role in cell cycle progression, spindle dynamics, and chromosome segregation. It is also involved in regulating apoptosis mediated by Fas or the retinoid X receptor (RXR), and is a positive regulator of Wnt signaling. CK1alpha phosphorylates the NS5A protein of flaviviruses such as the Hepatitis C virus (HCV) and yellow fever virus (YFV), and influences flaviviral replication. The CK1 alpha 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.
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