STK40 Is a Pseudokinase that Binds the E3 Ubiquitin Ligase COP1

Structure. 2017 Feb 7;25(2):287-294. doi: 10.1016/j.str.2016.12.008. Epub 2017 Jan 12.

Abstract

Serine/threonine kinase 40 (STK40) was originally identified as a distant homolog of Tribbles-family proteins. Despite accumulating data attesting to the importance of STK40 in a variety of different physiologic processes, little is known about its biological activity or mechanism of action. Here, we show that STK40 interacts with Constitutive Photomorphogenic Protein 1 (COP1), relying primarily on a C-terminal sequence analogous to the motif found in Tribbles proteins. In order to further elucidate structure-function relationships in STK40, we determined the crystal structure of the STK40 kinase homology domain at 2.5 Å resolution. The structure, together with ATP-binding assay results, show that STK40 is a pseudokinase, in which substitutions of conserved residues within the kinase domain prevent ATP binding. Although the structure of the kinase homology domain diverges from the analogous region of Trib1, the results reported here suggest functional parallels between STK40 and Tribbles-family proteins as COP1 adaptors.

Keywords: ATP binding; COP1; E3 ligase; RFWD2; SINK-homologous kinase; STK40; SgK495; Tribbles; X-ray crystallography; pseudokinase.

MeSH terms

  • Adenosine Triphosphate / chemistry*
  • Adenosine Triphosphate / metabolism
  • Amino Acid Sequence
  • Catalytic Domain
  • Cloning, Molecular
  • Crystallography, X-Ray
  • Gene Expression
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Intracellular Signaling Peptides and Proteins / chemistry*
  • Intracellular Signaling Peptides and Proteins / genetics
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Models, Molecular
  • Protein Binding
  • Protein Conformation, alpha-Helical
  • Protein Conformation, beta-Strand
  • Protein Interaction Domains and Motifs
  • Protein-Serine-Threonine Kinases / antagonists & inhibitors*
  • Protein-Serine-Threonine Kinases / chemistry
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Substrate Specificity
  • Ubiquitin-Protein Ligases / chemistry*
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism

Substances

  • Intracellular Signaling Peptides and Proteins
  • Recombinant Proteins
  • TRIB1 protein, human
  • Adenosine Triphosphate
  • COP1 protein, human
  • Ubiquitin-Protein Ligases
  • Protein-Serine-Threonine Kinases
  • STK40 protein, human