Structures of imatinib and dasatinib bound to Abl kinase. (A) View of imatinib (gold) in complex with the Abl kinase domain, in which the activation loop (cyan) is in the “closed” position and the ATP binding loop (magenta) is distorted downward relative to the ATP-bound state. (B) View of dasatinib (gold) in complex with the Abl kinase domain. The activation loop (cyan) is in the “open” position and the ATP binding loop is shown in magenta. In both panels, an arrow denotes the position of Abl residue threonine-315 (side chain in green). For both inhibitors, oxygen (red) and nitrogen (blue) atoms are highlighted.