Cryo-EM structure of a dimeric B-Raf:14-3-3 complex reveals asymmetry in the active sites of B-Raf kinases

Science. 2019 Oct 4;366(6461):109-115. doi: 10.1126/science.aay0543. Epub 2019 Sep 19.


Raf kinases are important cancer drug targets. Paradoxically, many B-Raf inhibitors induce the activation of Raf kinases. Cryo-electron microscopy structural analysis of a phosphorylated B-Raf kinase domain dimer in complex with dimeric 14-3-3, at a resolution of ~3.9 angstroms, shows an asymmetric arrangement in which one kinase is in a canonical "active" conformation. The distal segment of the C-terminal tail of this kinase interacts with, and blocks, the active site of the cognate kinase in this asymmetric arrangement. Deletion of the C-terminal segment reduces Raf activity. The unexpected asymmetric quaternary architecture illustrates how the paradoxical activation of Raf by kinase inhibitors reflects an innate mechanism, with 14-3-3 facilitating inhibition of one kinase while maintaining activity of the other. Conformational modulation of these contacts may provide new opportunities for Raf inhibitor development.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 14-3-3 Proteins / chemistry*
  • 14-3-3 Proteins / metabolism
  • Animals
  • Catalytic Domain
  • Cell Line
  • Cryoelectron Microscopy
  • Humans
  • Insect Proteins / chemistry
  • Insect Proteins / metabolism
  • Mice
  • Models, Molecular
  • Molecular Dynamics Simulation
  • Mutation
  • Phosphorylation
  • Protein Domains
  • Protein Multimerization
  • Proto-Oncogene Proteins B-raf / chemistry*
  • Proto-Oncogene Proteins B-raf / genetics
  • Proto-Oncogene Proteins B-raf / metabolism
  • Spodoptera


  • 14-3-3 Proteins
  • Insect Proteins
  • BRAF protein, human
  • Proto-Oncogene Proteins B-raf