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Structural insights into the recognition of substrates and activators by the OSR1 kinase

Fabrizio Villa1, Jürgen Goebel, Fatema H Rafiqi

  • 1Division of Biological Chemistry and Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK.

EMBO Reports
|August 28, 2007
PubMed

Insights

The carboxy-terminal domain of OSR1 kinase recognizes specific peptide motifs in WNK kinases and NKCC transporters. This structural insight reveals how OSR1 and SPAK kinases bind activators and substrates.

Area of Science:

  • Molecular Biology
  • Structural Biology
  • Biochemistry

Background:

  • Oxidative-stress-responsive kinase 1 (OSR1) and STE20/SPS1-related proline/alanine-rich kinase (SPAK) regulate Na(+)/K(+)/2Cl(-) co-transporters (NKCCs) activity during osmotic stress.
  • Both OSR1 and SPAK possess a conserved carboxy-terminal (CCT) domain crucial for recognizing specific peptide motifs.

Purpose of the Study:

  • To elucidate the structural basis of the OSR1 CCT domain's recognition of the Arg-Phe-Xaa-Val motif.
  • To understand the molecular interactions governing the binding of upstream activators (WNK kinases) and downstream substrates (NKCCs).

Main Methods:

  • X-ray crystallography to determine the structure of the OSR1 CCT domain in complex with a WNK4-derived peptide.
  • Mutational analysis to assess the functional importance of observed interactions.

Main Results:

  • The OSR1 CCT domain adopts a novel fold that binds the Arg-Phe-Xaa-Val motif via a surface groove.
  • Detailed molecular interactions between the OSR1 CCT domain and the WNK4 peptide were elucidated.
  • Mutational studies confirmed the necessity of these interactions for binding WNK1 and NKCC1.
  • The structure explains how preceding phosphorylation events disrupt binding through steric clashes.

Conclusions:

  • This study provides the first molecular insights into the specific recognition mechanism of OSR1 and SPAK kinases for their activators and substrates.
  • The findings are critical for understanding the regulation of NKCC activity in response to osmotic stress.

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