Figure 6.

Binding preferences of conformation-selective, ATP-competitive inhibitors. (A) Ligands that stabilize the DFG-out and αC helix-out conformations make a number of different interactions with the ATP-binding sites of kinases. Left: Src bound to 3 with the ATP-binding site in an inactive, αC helix-out conformation (PDB: 4DGG). The αC helix is rotated out of the active site, disrupting the interaction between Lys295 and Glu310. Right: Abl bound to 5 with the active site in an inactive, DFG-out conformation (PDB: 3OXZ). The DFG motif is flipped out of the active site, but Glu310 in the αC helix maintains a salt bridge with the catalytic lysine (the distance between the NH of 5 and the Glu310 side chain is 3.0 Å). The gatekeeper (Thr338), catalytic lysine (Lys295), and catalytic glutamic acid (Glu310) residues are shown in light blue (Src numbering). (B) Analogues of 3 that were tested in activity assays against Src^act, Hck^act, Src^SH2eng, and Hck^SH2eng constructs. Quantitative comparison of the fold differences in K_i values between activated SFKs (SFK^act) and their respective autoinhibited constructs (SFK^SH2eng) allow systematic analysis of ATP-binding site conformational preference. Raw data for all assays are shown in Supporting Information Table S5.