Receptor preparation and SiteMap analysis. Structures of SurA (PDB-ID 1m5y, chain A) and GAK (PDB-ID 4y8d, chain A) were retrieved from the RCSB Protein Data Bank. The Schrödinger Protein Preparation Wizard was used for structure preparation, hydrogen addition, and bond order assignment. Missing sidechains were added with Prime. Crystallographic agents and water molecules were deleted. State generation for the original crystallographic ligand in the GAK structure was performed with Epik for pH 7.0±2.0. Amino acid protonation states for pH 7.0 were assigned with PROPKA and the hydrogen bonding network was optimized. Receptors were then subjected to a restrained energy minimization in the OPLS_2005 forcefield until the heavy atom RMSD compared to the previous minimization step fell below 0.3 Å.