Multiple Solvent Crystal Structures (MSCS) is a crystallographic technique to
identify energetically favorable positions and orientations of small organic
molecules on the surface of proteins. We determined the high-resolution crystal
structures of thermolysin (TLN), generated from crystals soaked in 50--70%
acetone, 50--80% acetonitrile and 50 mM phenol. The structures of the protein in
the aqueous-organic mixtures are essentially the same as the native enzyme and a
number of solvent interaction sites were identified. The distribution of probe
molecules shows clusters in the main specificity pocket of the active site and a
buried subsite. Within the active site, we compared the experimentally
determined solvent positions with predictions from two computational functional
group mapping techniques, GRID and Multiple Copy Simultaneous Search (MCSS). The
experimentally determined small molecule positions are consistent with the
structures of known protein--ligand complexes of TLN.
