Crystal structure of the complex of concanavalin A and tripeptide

The X-ray structure analysis of a cross-linked crystal of concanavalin A so aked with the tripeptide molecule as the probe molecule showed electron den sity corresponding to full occupation in the binding pocket. The site lies on the surface of concanavalin A and is surrounded by three symmetry-relate d molecules. The crystal structure of the tripeptide complex was refined at 2.4-Angstrom resolution to an R-factor of 17.5%, (R-free factor of 23.7%), with an RMS deviation in bond distances of 0.01 Angstrom. The model includ es all 237 residue of concanavalin A, 1 manganese ion, 1 calcium ion, 161 w ater molecules, 1 glutaraldehyde molecule, and 1 tripeptide molecule. This X-ray structure analysis also provides an approach to mapping the binding s urface of crystalline protein with a probe molecule that is dissolved in a mixture of organic solvent with water or in neat organic solvent but is har dly dissolved in aqueous solution.