Abstract
The binding of SPAK and OSR1 kinases to their upstream WNK kinases is mediated by the interaction of their highly conserved SPAK and OSR1 C-terminal domain (CTD) to RFx [V/I] peptide sequences from WNK kinases. A SPAK CTD knock-in mouse, where SPAK was unable to bind WNK kinases, exhibited low blood pressure. This highlighted the inhibition of SPAK and OSR1 kinases binding to their upstream WNK kinases as a plausible strategy in the discovery of new antihypertensive agents. To facilitate such endeavour, we herein report the optimisation and expression of isotopically labelled OSR1 CTD in E.coli and a structural model based on the sequence specific NMR assignments giving insights into the structure of apo OSR1 CTD. Additionally, we identified the OSR1 CTD amino acid residues that are important for the binding of an 18-mer RFQV peptide derived from human WNK4. Collectively, the NMR backbone assignments and the generated OSR1 CTD 3D model reported in this work will be a powerful resource for the NMR-based discovery of small molecule OSR1 (and SPAK) kinase inhibitors as potential antihypertensive agents.
•15N-isotopically labelled OSR1 CTD expressed in E.coli is stable and well folded.•The first apo structure of OSR1 CTD is reported.•The NMR-derived OSR1 CTD 3D structure has a very similar folding pattern to OSR1 CTD crystal structure.•Twelve amino acid residues in OSR1 CTD were identified to be involved in the binding to a WNK4-derived peptide.