Protein binding sites undergo ligand specific conformational changes upon ligand binding. However, most docking protocols
rely on a fixed conformation of the receptor, or on the prior knowledge of multiple conformations representing the variation
of the pocket, or on a known bounding box for the ligand. Here we described a general induced fit docking protocol that requires
only one initial pocket conformation and identifies most of the correct ligand positions as the lowest score. We expanded
a previously used diverse “cross-docking” benchmark to thirty ligand–protein pairs extracted from different crystal structures.
The algorithm systematically scans pairs of neighbouring side chains, replaces them by alanines, and docks the ligand to each
‘gapped’ version of the pocket. All docked positions are scored, refined with original side chains and flexible backbone and
re-scored. In the optimal version of the protocol
pairs of residues were replaced by alanines and only
one best scoring conformation was selected from each ‘gapped’ pocket for refinement. The optimal SCARE (SCan Alanines and REfine)
protocol identifies a near native conformation (under 2 Å RMSD) as the lowest rank for 80% of pairs if the docking bounding
box is defined by the
predicted pocket envelope, and for as many as 90% of the pairs if the bounding box is derived from the known answer with ∼5 Å margin
as used in most previous publications. The presented fully automated algorithm takes about 2 h per pose of a single processor
time, requires only one pocket structure and no prior knowledge about the binding site location. Furthermore, the results
for conformationally conserved pockets do not deteriorate due to substantial increase of the pocket variability.
Keywords Scanning docking - Cross docking - ICM - Internal coordinate mechanics - Induced fit - Receptor flexibility - Drug binding - Structure based drug design