DRAMATIC SACCHARIDE-MEDIATED PROTECTION OF CHAOTROPIC-INDUCED DEACTIVATION OF CONCANAVALIN-A

This work provides evidence of a physical instance in which some prote ins that are usually inactivated under strong chaotropic conditions ma y become fully resistant through the occupancy of their binding sites with suitable ligands. In this regard, we found that Moluccella laevis lectin remains stable in the presence of denaturant concentrations of urea when an appropriate saccharide is bound to the protein (Alperin, D. M., Latter, H., Lis, H., and Sharon, N. (1992) Biochem. J. 285, 1- 4). Extending this finding, we now demonstrate that the occupancy of t he ligand binding sites of concanavalin A (Con A) with appropriate car bohydrates completely prevents the denaturation course elicited by 8 M urea at pH 7.4, In addition, the protecting efficiency of the sacchar ides was shown to be directly related to their specificities for the l ectin. The observed saccharide protection follows the order: methyl al pha-D-mannopyranoside > methyl alpha-D-glucopyranoside > mannose > fru ctose > glucose, Concomitantly, the active tetrameric lectin with a mo lecular mass of similar to 105 kDa is preserved in 8 M urea when methy l alpha-D-mannopyranoside (100 mM) is present in the medium. (C) 1997 Academic Press.