(A) Close-up of the 4MNE structure indicating the salt bridge between Arg575 and Glu611 that is conserved in all Raf kinases. Lys601 points in the direction of this salt bridge. (B) Superimposition of all BRAF kinases that are solved at K601. For 4MNE, the ribbon representation is shown in grey, and the residues are as in panel (A). For the remaining structures, only the backbone and side chain of K601 is shown. The structural representations were made using SwissPdbViewer (PDB entries 4MNE, 1UWJ, 3TV4, 4E4X, 4EHE, 4G9R, 4PP7, 4JVG, 4MBJ, 4H58, 3Q4C, 4E26, and 4G9C). (C) Overlay of 10 active-like BRAF structures. Residues 597–600 (red) are very similar between the different structures, while resides 601–616 (blue) are more flexible. The structural representation was made using SwissPdbViewer (PDB entries 2FB8, 3D4Q, 3OG7, 3PPJ, 3PPK, 3PRI, 3PSB, 4H58, 4MNE, and 4MNF).