The number of fragments per subpocket is reported in Figure .B and Table . Containing 35.6% of the 7,201 fragments (excluding pool X), AP is the most frequently occupied subpocket. Remember that by design this study focuses on ligands covering the AP subpocket, and all ligands not occupying AP were discarded beforehand. Also note that AP contains 8 fragments more than the actual number of fragmented ligands, i.e. 2,553. This is possible because the fragmentation algorithm allows that two not neighboring fragments of a ligand occupy the same subpocket, since not all ligands perfectly fit to the defined subpockets (this happens only rarely). The second most occupied subpocket is FP (25.9% of fragments), followed by SE (21.7%) and GA (14.2%). The back pockets B1 and B2 are occupied by only 2.6% of the fragments in total. According to this, known type I and I 1 /2 kinase ligands mostly target the same subpockets as the kinase substrate ATP (AP and (Left) Subpockets and allowed connections with solid/dotted lines if present/not present in example ligand, including frequency of ligands with highlighted connection. (Middle) ligand conformation in kinase structure, including subpocket centers (spheres).