Molecule of the Month: RAF Protein Kinases
A single mutation in a RAF protein kinase can help transform a normal cell into a cancer cell.
Sending the Signal
RAS to RAF
RAF to MEK
Exploring the Structure
BRAF with Anticancer Drugs (PDB entries 4xv2, 3og7 and 4xv1)
Knowledge of the structure of mutated BRAF allowed researchers to design drugs to block it, thereby curbing the unnatural growth of cancer cells. These drugs work very well on some types of cancer, such as melanoma, but can actually promote growth in some other cancers. When researchers looked more deeply, they found that this was caused by an unusual interaction: sometimes BRAF and CRAF form a heterodimer, and the drug was only attacking BRAF. This challenge was overcome by using higher levels of drug to block both forms, and researchers are now working on second generation drugs that block RAF from dimerizing and becoming active. Take a look at the interactive JSmol to compare the structures of three drugs: Vemurafenib (shown here from PDB entry 3og7), Dabrafenib (PDB entry 4xv2) and the experimental drug PLX7904 (PDB entry 4xv1).
Topics for Further Discussion
- You can used the Protein Feature View for BRAF to explore how the structures of RAF domains fit into the overall sequence of the protein.
- Many drugs that attack RAF proteins are designed to mimic ATP, since ATP is essential for the phosphorylation reaction. Try to identify the portions of the drugs in the JSmol that mimic the ATP base and the ATP phosphate.
Related PDB-101 Resources
- Browse Cancer
- Browse Cellular Signaling
- 4xv1, 4xv2: C. Zhang, W. Spevak, Y. Zhang, E. A. Burton, Y. Ma, G. Habets, J. Zhang, J. Lin, T. Ewing, B. Matusow, G. Tsang, A. Marimuthu, H. Cho, G. Wu, W. Wang, D. Fong, H. Nguyen, S. Shi, P. Womack, M. Nespi, R. Shellooe, H. Carias, B. Powell, E. Light, L. Sanftner, J. Walters, J. Tsai, B. L. West, G. Visor, H. Rezaei, P. S. Lin, K. Nolop, P. N. Ibrahim, P. Hirth & G. Bollag (2015) RAF inhibitors that evade paradoxical MAPK pathway activation. Nature 526, 583-586.
- 4mne: J. R. Haling, J. Sudhamsu, I. Yen, S. Sideris, W. Sandoval, W. Phung, B. J. Bravo, A. M. Giannetti, A. Peck, A. Masselot, T. Morales, D. Smith, B. J. Brandhuber, S. G. Hymowitz & S. Malek (2014) Structure of the BRAF-MEK complex reveals a kinase activity independent role for BRAF in MAPK signaling. Cancer Cell 26, 402-413.
- 3og7: G. Bollag, P. Hirth, J. Tsai, J. Zhang, P. N. Ibrahim, H. Cho, W. Spevak, C. Zhang, Y. Zhang, G. Habets, E. A. Burton, B. Wong, G. Tsang, B. L. West, B. Powell, R. Shellooe, A. Marimuthu, H. Nguyen, K. Y. Zhang, D. R. Artis, J. Schlessinger, F. Su, B. Higgins, R. Iyer, K. D’Andrea, A. Koehler, M. Stumm, P. S. Lin, J. Grippo, I. Puzanov, K. B. Kim, A. Ribas, G. A. McArthur, J. A. Sosman, P. B. Chapman, K. T. Flaherty, X. Xu, K. L. Nathanson & K. Nolop (2010) Clinical efficacy of a RAF inhibitor needs broad target blockade in BRAF-mutant melanoma. Nature 467, 596-599.
- 3kud: D. Filchtinski, O. Sharabi, A. Ruppel, I. R. Vetter, C. Herrmann & J. M. Shifman (2010) What make Ras an efficient molecular switch: a computational, biophysical, and structural study of Ras-GDP interactions with mutants of Raf. Journal of Molecular Biology 399, 422-435.
- 1uwh: P. T. C. Wan, M. J. Garnett, S. M. Roe, S. Lee, D. Niculescu-Duvaz, V. M. Good, C. M. Jones, C. J. Marshall, D. Barford & R. Marais (2004) Mechanism of activation of the Raf-Erk signaling pathway by oncogenic mutations of B-Raf. Cell 116, 855-867.
- C. Wellbrock, M. Karasarides & R. Marais (2004) The Raf proteins take centre stage. Nature Reviews Molecular Cell Biology 5, 875-885.
- 1far: H. R. Mott, J. W. Carpenter, S. Zhong, S. Ghosh, R. M. Bell & S. L. Campbell (1996) The solution structure of the Raf-1 cysteine-rich domain: a novel ras and phospholipid binding site. Proceedings of the National Academy of Science USA 93, 8312-8317.
March 2016, David Goodsellhttp://doi.org/10.2210/rcsb_pdb/mom_2016_3