Concatenation of 14-3-3 with partner phosphoproteins as a tool to study their interaction

Sci Rep. 2019 Oct 18;9(1):15007. doi: 10.1038/s41598-019-50941-3.

Abstract

Regulatory 14-3-3 proteins interact with a plethora of phosphorylated partner proteins, however 14-3-3 complexes feature intrinsically disordered regions and often a transient type of interactions making structural studies difficult. Here we engineer and examine a chimera of human 14-3-3 tethered to a nearly complete partner HSPB6 which is phosphorylated by protein kinase A (PKA). HSPB6 includes a long disordered N-terminal domain (NTD), a phosphorylation motif around Ser16, and a core α-crystallin domain (ACD) responsible for dimerisation. The chosen design enables an unstrained binding of pSer16 in each 1433 subunit and secures the correct 2:2 stoichiometry. Differential scanning calorimetry, limited proteolysis and small-angle X-ray scattering (SAXS) support the proper folding of both the 14-3-3 and ACD dimers within the chimera, and indicate that the chimera retains the overall architecture of the native complex of 14-3-3 and phosphorylated HSPB6 that has recently been resolved using crystallography. At the same time, the SAXS data highlight the weakness of the secondary interface between the ACD dimer and the C-terminal lobe of 14-3-3 observed in the crystal structure. Applied to other 14-3-3 complexes, the chimeric approach may help probe the stability and specificity of secondary interfaces for targeting them with small molecules in the future.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 14-3-3 Proteins / metabolism*
  • Calorimetry, Differential Scanning
  • Crystallization
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • HSP20 Heat-Shock Proteins / metabolism
  • Hot Temperature
  • Humans
  • Models, Molecular*
  • Phosphoproteins / metabolism*
  • Phosphorylation
  • Protein Conformation, alpha-Helical
  • Protein Domains
  • Protein Multimerization
  • Protein Unfolding
  • Proteolysis
  • Scattering, Small Angle
  • X-Ray Diffraction
  • alpha-Crystallins / metabolism

Substances

  • 14-3-3 Proteins
  • HSP20 Heat-Shock Proteins
  • HSPB6 protein, human
  • Phosphoproteins
  • alpha-Crystallins