Fig. 5. The stabilized R-spine of LLR^ins506 or VLR^ins506 mutants impairs RAF inhibitor association, which also occurs in other BRAF mutants with stabilized R-spine.

(A) Docking poses of vemurafenib, dabrafenib, and PLX8394 on BRAF with an intact (yellow) or broken (purple) R-spine. Configurations of intact and broken R-spine were shown in stick representation with translucent surfaces, while the ligands only in stick representation. (B) RAF inhibitors have much less affinity with LLR^ins506 mutant than BRAF(V600E). The apparent dissociation constant values were measured by using MST method in buffer with 1 mM adenosine 5′-triphosphate. (C to E) BRAF(L505H) and BRAF(L485F) that have enhanced R-spine exhibited similar resistance to RAF inhibitors. The drug response of 293T transfectants that express individual BRAF mutants was determined as in Fig. 4 (A to E). All images are representative of at least three independent experiments.