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Structures of the Human SPAK and OSR1 Conserved C-Terminal (CCT) Domains

Elvers, Karen T.; Lipka-Lloyd, Magdalena; Trueman, Rebecca C.; Bax, Benjamin D.; Mehellou, Youcef

Structures of the Human SPAK and OSR1 Conserved C-Terminal (CCT) Domains Thumbnail


Karen T. Elvers

Magdalena Lipka-Lloyd

Benjamin D. Bax

Youcef Mehellou


STE20/SPS1-related proline/alanine-rich kinase (SPAK) and oxidative stress responsive 1 (OSR1) kinase are two serine/threonine protein kinases that regulate the function of ion co-transporters through phosphorylation. The highly conserved C-terminal (CCT) domains of SPAK and OSR1 bind to RFx[V/I] peptide sequences from their upstream ‘With No Lysine Kinases (WNKs), facilitating their activation via phosphorylation. Thus, the inhibition of SPAK and OSR1 binding, via their CCT domains, to WNK kinases is a plausible strategy for inhibiting SPAK and OSR1 kinases. To facilitate structure-guided drug design of such inhibitors, we expressed and purified human SPAK and OSR1 CCT domains and solved their crystal structures. Interestingly, these crystal structures show a highly conserved primary pocket adjacent to a flexible secondary pocket. We also employed a biophysical strategy and determined the affinity of SPAK and OSR1 CCT domains to short peptides derived from WNK4 and NKCC1. Together, this work provides a platform that facilitates the design of CCT domain specific small molecule binders that inhibit SPAK- and OSR1-activation by WNK kinases, and these could be useful in treating hypertension and ischemic stroke.


Elvers, K. T., Lipka-Lloyd, M., Trueman, R. C., Bax, B. D., & Mehellou, Y. (2022). Structures of the Human SPAK and OSR1 Conserved C-Terminal (CCT) Domains. ChemBioChem, 23(1),

Journal Article Type Article
Acceptance Date Nov 2, 2021
Online Publication Date Nov 24, 2021
Publication Date Jan 5, 2022
Deposit Date Nov 30, 2021
Publicly Available Date Nov 25, 2022
Journal ChemBioChem
Print ISSN 1439-4227
Electronic ISSN 1439-7633
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 23
Issue 1
Article Number e202100441
Keywords Organic Chemistry; Molecular Biology; Molecular Medicine; Biochemistry
Public URL
Publisher URL
Additional Information This is the peer reviewed version of the following article: Elvers, K.T., Lipka-Lloyd, M., Trueman, R.C., Bax, B.D. and Mehellou, Y. (2021), Structures of the Human SPAK and OSR1 Conserved C-Terminal (CCT) Domains** . ChemBioChem., which has been published in final form at This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.


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