Figure 4.

BRAF kinase in an active conformation. (a) Superposition of the BRAF–CS292 complex protein fragment with the PKA–ATP complex (PDBentry 1ATP). The BRAF kinase is colored blue and PKA green. Essential catalytic residues are shown in stick figure representation with color coding corresponding to each kinase. Magnesium ions are shown as magenta spheres, and hydrogen bonding interactions are shown as blue dashes. Part of the activation loop is truncated for better viewing of the PKA phospho-Thr197. (b) Superposition of the BRAF–CS292 complex with BRAF in an active conformation with the BRAF–Sorafenib complex in an inactive conformation. The BRAF–CS292 complex is colored blue and the BRAF–Sorafenib complex red. (c) ATP K_m measurements of BRAF^V600E and BRAF^WT kinases and effect of K507A and R575A mutations on K_m,ATP. The reaction rate is normalized against the V_max of each kinase construct, and K_m values are extrapolated from a sigmoidal curve fitting model and listed in units of micromolar. All compounds were used as racemic mixtures.