Modification of bovine beta-lactoglobulin by glycation in a powdered stateor in an aqueous solution: Effect on association behavior and protein conformation

The effect of glycation with lactose on the association behavior and confor mational state of bovine beta-lactoglobulin (beta-LG) was studied, using si ze exclusion chromatography, polyacrylamide gel electrophoresis, proteolyti c susceptibility, and binding of a. fluorescent probe. Two modification tre atments were used, i.e., aqueous solution glycation and dry-way glycation. The results showed that the latter treatment did not significantly alter th e nativelike behavior of the protein while the former treatment led to impo rtant structural changes. These changes resulted in a specific denatured be ta-LG monomer, which covalently associated via the free thiol group. The ho modimers thus formed and the expanded monomers underwent subsequent aggrega tion into a high molecular weight species; via noncovalent interactions. Th e association behavior of glycated beta-LG is discussed with respect to the known multistep denaturation/aggregation process of nonmodified beta-LG.