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Catalytic domain of the Serine/Threonine kinase, With No Lysine (WNK) kinase STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. WNKs comprise a subfamily of STKs with an unusual placement of a catalytic lysine relative to all other protein kinases. They are critical in regulating ion balance and are thus, important components in the control of blood pressure. They are also involved in cell signaling, survival, proliferation, and organ development. WNKs are activated by hyperosmotic or low-chloride hypotonic stress and they function upstream of SPAK and OSR1 kinases, which regulate the activity of cation-chloride cotransporters through direct interaction and phosphorylation. There are four vertebrate WNKs which show varying expression patterns. WNK1 and WNK2 are widely expressed while WNK3 and WNK4 show a more restricted expression pattern. Because mutations in human WNK1 and WNK4 cause PseudoHypoAldosteronism type II (PHAII), characterized by hypertension (due to increased sodium reabsorption) and hyperkalemia (due to impaired renal potassium secretion), there are more studies conducted on these two proteins, compared to WNK2 and WNK3. The WNK 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. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",