Copper-catalyzed formation of disulfide-linked dimer of bovine β-lactoglobulin

Under denaturing conditions, copper was shown to induce dimerization of bovine beta-lactoglobulin (beta-Lg). The occurrence of this chemical reaction and the characterization of the species formed were investigated under various experimental conditions. When beta-Lg solution was heated or treated with a denaturant in the presence of copper, covalent dimerization through oxidation of SH groups was observed. The rate of dimer formation increased with increased concentration of both copper and denaturant. The copper-dependent conversion rate of native protein into the covalently-linked dimer was found to be seven to ten-fold faster for variant B than for variant A. The functional and biological implications of the copper-modified beta-Lg are discussed.