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

Allosteric activation of functionally asymmetric RAF kinase dimers.

Author information

1
Department of Pathology and Immunology, Washington University School of Medicine, 660 South Euclid, Box 8118, St. Louis, MO 63110, USA; Howard Hughes Medical Institute, Washington University School of Medicine, 660 South Euclid, Box 8118, St. Louis, MO 63110, USA.
2
Department of Pathology and Immunology, Washington University School of Medicine, 660 South Euclid, Box 8118, St. Louis, MO 63110, USA.
3
Department of Chemistry/Biochemistry, University of California San Diego, 9500 Gilman Drive, Mail code 0654, La Jolla, CA 92093, USA; Department of Pharmacology, University of California San Diego, 9500 Gilman Drive, Mail code 0654, La Jolla, CA 92093, USA.
4
Vollum Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA.
5
Department of Chemistry/Biochemistry, University of California San Diego, 9500 Gilman Drive, Mail code 0654, La Jolla, CA 92093, USA; Department of Pharmacology, University of California San Diego, 9500 Gilman Drive, Mail code 0654, La Jolla, CA 92093, USA; Howard Hughes Medical Institute, University of California San Diego, 9500 Gilman Drive, Mail code 0654, La Jolla, CA 92093, USA.
6
Department of Chemistry/Biochemistry, University of California San Diego, 9500 Gilman Drive, Mail code 0654, La Jolla, CA 92093, USA; Department of Pharmacology, University of California San Diego, 9500 Gilman Drive, Mail code 0654, La Jolla, CA 92093, USA; Howard Hughes Medical Institute, University of California San Diego, 9500 Gilman Drive, Mail code 0654, La Jolla, CA 92093, USA. Electronic address: staylor@ucsd.edu.
7
Department of Pathology and Immunology, Washington University School of Medicine, 660 South Euclid, Box 8118, St. Louis, MO 63110, USA; Howard Hughes Medical Institute, Washington University School of Medicine, 660 South Euclid, Box 8118, St. Louis, MO 63110, USA. Electronic address: ashaw@wustl.edu.

Abstract

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.

PMID:
23993095
PMCID:
PMC3844432
DOI:
10.1016/j.cell.2013.07.046
[Indexed for MEDLINE]
Free PMC Article

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