9znm
WNK1/SA kinase domain in complex with potassium formate at 1 Angstrom wavelength
Structural highlights
FunctionWNK1_RAT Serine/threonine kinase which plays an important role in the regulation of electrolyte homeostasis, cell signaling, survival and proliferation. Acts as an activator and inhibitor of sodium-coupled chloride cotransporters and potassium-coupled chloride cotransporters respectively. Activates SCNN1A, SCNN1B, SCNN1D and SGK1. Controls sodium and chloride ion transport by inhibiting the activity of WNK4, by either phosphorylating the kinase or via an interaction between WNK4 and the autoinhibitory domain of WNK1. WNK4 regulates the activity of the thiazide-sensitive Na-Cl cotransporter, SLC12A3, by phosphorylation. WNK1 may also play a role in actin cytoskeletal reorganization. Phosphorylates NEDD4L.[1] [2] Publication Abstract from PubMedWNK kinases are chloride- and osmotic-stress-regulated protein kinases recently shown to be controlled by potassium. Prior studies demonstrated the direct binding of chloride and osmotic stress-related water in WNK kinase regulation. Here, we probe potassium binding and regulation of WNK kinases via crystallography coupled with mutagenic analysis of WNK kinase autophosphorylation and activity. Crystals of unphosphorylated WNK1 grown in cesium formate, a surrogate for potassium, yielded nonsulfur scattering peaks at 5.75 keV. Mutations were introduced into amino acids flanking the anomalous diffraction peaks. Mutations in WNK1/E388 and the corresponding WNK3/E314, probing a peak close to WNK1/I384, led to reduced inhibition by potassium while maintaining kinase autophosphorylation and substrate phosphorylation activity. Other peaks probed by mutagenesis either did not bear out as potassium regulatory sites or were not validated due to the inactivity of the mutants synthesized. Previously synthesized chloride- and water-binding mutants demonstrate correlated sensitivity to chloride and potassium. Potassium, chloride, and water are all WNK inhibitors that share a common mechanism binding the same low-activity asymmetric dimer of WNK1 kinase domains. Structural Basis for Potassium Inhibition of WNK Kinases.,Goldsmith EJ, Pleinis JM, Wagner A, Mykhaylyk V, Akella R, Humphreys JM, He H, Norrell L, Morrison DE, Rodan AR Biochemistry. 2026 Jun 16;65(12):1922-1931. doi: 10.1021/acs.biochem.5c00825. , Epub 2026 May 26. PMID:42186973[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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