5JSM: Brafv600e Kinase Domain In Complex With Chemically Linked Vemurafenib Inhibitor Vem-3-vem

Citation:
Abstract
The BRAF kinase, within the mitogen activated protein kinase (MAPK) signaling pathway, harbors activating mutations in about half of melanomas and to a significant extent in many other cancers. A single valine to glutamic acid substitution at residue 600 (BRAFV600E) accounts for about 90% of these activating mutations. While BRAFV600E-selective small molecule inhibitors, such as debrafenib and vemurafenib, have shown therapeutic benefit, almost all patients develop resistance. Resistance often arises through reactivation of the MAPK pathway, typically through mutation of upstream RAS, downstream MEK, or splicing variants. RAF kinases signal as homo- and heterodimers, and another complication associated with small molecule BRAFV600E inhibition is drug-induced allosteric activation of a wild-type RAF subunit (BRAF or CRAF) of the kinase dimer, a process called "transactivation" or "paradoxical activation." Here, we used BRAFV600E and vemurafenib as a model system to develop chemically linked kinase inhibitors to lock RAF dimers in an inactive conformation that cannot undergo transactivation. This structure-based design effort resulted in the development of Vem-BisAmide-2, a compound containing two vemurafenib molecules connected by a bis amide linker. We show that Vem-BisAmide-2 has comparable inhibitory potency as vemurafenib to BRAFV600E both in vitro and in cells but promotes an inactive dimeric BRAFV600E conformation unable to undergo transactivation. The crystal structure of a BRAFV600E/Vem-BisAmide-2 complex and associated biochemical studies reveal the molecular basis for how Vem-BisAmide-2 mediates selectivity for an inactive over an active dimeric BRAFV600E conformation. These studies have implications for targeting BRAFV600E/RAF heterodimers and other kinase dimers for therapy.
PDB ID: 5JSMDownload
MMDB ID: 143095
PDB Deposition Date: 2016/5/8
Updated in MMDB: 2016/11
Experimental Method:
x-ray diffraction
Resolution: 2.19  Å
Source Organism:
Similar Structures:
Biological Unit for 5JSM: dimeric; determined by author
Molecular Components in 5JSM
Label Count Molecule
Proteins (2 molecules)
2
Serine/threonine-protein Kinase B-raf(Gene symbol: BRAF)
Molecule annotation
Chemicals (11 molecules)
1
4
2
2
3
1
4
3
5
1
* Click molecule labels to explore molecular sequence information.

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