5d9h
Crystal structure of SPAK (STK39) dimer in the basal activity stateCrystal structure of SPAK (STK39) dimer in the basal activity state
Structural highlights
FunctionSTK39_MOUSE May act as a mediator of stress-activated signals. Mediates the inhibiton of SLC4A4, SLC26A6 as well as CFTR activities by the WNK scaffolds, probably through phosphorylation (PubMed:21317537, PubMed:23542070).[1] [2] Publication Abstract from PubMedThe related protein kinases SPAK and OSR1 regulate ion homeostasis in part by phosphorylating cation cotransporter family members. The structure of the kinase domain of OSR1 was determined in the unphosphorylated inactive form and, like some other Ste20 kinases, exhibited a domain-swapped activation loop. To further probe the role of domain swapping in SPAK and OSR1, we have determined the crystal structures of SPAK 63-403 at 3.1 A and SPAK 63-390 T243D at 2.5 A resolution. These structures encompass the kinase domain and different portions of the C-terminal tail, the longer without and the shorter with an activating T243D point mutation. The structure of the T243D protein reveals significant conformational differences relative to unphosphorylated SPAK and OSR1 but also has some features of an inactive kinase. Both structures are domain-swapped dimers. Sequences involved in domain swapping were identified and mutated to create a SPAK monomeric mutant with kinase activity, indicating that monomeric forms are active. The monomeric mutant is activated by WNK1 but has reduced activity toward its substrate NKCC2, suggesting regulatory roles for domain swapping. The structure of partially active SPAK T243D is consistent with a multistage activation process in which phosphorylation induces a SPAK conformation that requires further remodeling to build the active structure. Domain-Swapping Switch Point in Ste20 Protein Kinase SPAK.,Taylor CA 4th, Juang YC, Earnest S, Sengupta S, Goldsmith EJ, Cobb MH Biochemistry. 2015 Aug 18;54(32):5063-71. doi: 10.1021/acs.biochem.5b00593. Epub , 2015 Aug 3. PMID:26208601[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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