Allosteric activation of functionally asymmetric RAF kinase dimers

Cell. 2013 Aug 29;154(5):1036-1046. doi: 10.1016/j.cell.2013.07.046.


Although RAF kinases are critical for controlling cell growth, their mechanism of activation is incompletely understood. Recently, dimerization was shown to be important for activation. Here we show that the dimer is functionally asymmetric with one kinase functioning as an activator to stimulate activity of the partner, receiver kinase. The activator kinase did not require kinase activity but did require N-terminal phosphorylation that functioned allosterically to induce cis-autophosphorylation of the receiver kinase. Based on modeling of the hydrophobic spine assembly, we also engineered a constitutively active mutant that was independent of Ras, dimerization, and activation-loop phosphorylation. As N-terminal phosphorylation of BRAF is constitutive, BRAF initially functions to activate CRAF. N-terminal phosphorylation of CRAF was dependent on MEK, suggesting a feedback mechanism and explaining a key difference between BRAF and CRAF. Our work illuminates distinct steps in RAF activation that function to assemble the active conformation of the RAF kinase.

Publication types

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

MeSH terms

  • Allosteric Regulation
  • Amino Acid Motifs
  • Amino Acid Sequence
  • Animals
  • Cell Line
  • Dimerization
  • Enzyme Activation
  • Humans
  • Mice
  • Models, Molecular
  • Molecular Sequence Data
  • Mutation
  • Phosphorylation
  • Protein Conformation
  • Protein Kinases / chemistry
  • Protein Kinases / genetics
  • Protein Kinases / metabolism
  • Proto-Oncogene Proteins B-raf / chemistry
  • Proto-Oncogene Proteins B-raf / genetics
  • Proto-Oncogene Proteins B-raf / metabolism
  • Proto-Oncogene Proteins c-raf / chemistry
  • Proto-Oncogene Proteins c-raf / genetics
  • Proto-Oncogene Proteins c-raf / metabolism
  • Sequence Alignment
  • Tryptophan / metabolism
  • raf Kinases / chemistry*
  • raf Kinases / genetics
  • raf Kinases / metabolism*


  • Tryptophan
  • Protein Kinases
  • KSR-1 protein kinase
  • Proto-Oncogene Proteins B-raf
  • Proto-Oncogene Proteins c-raf
  • raf Kinases