к-Casein (к-C) and β-lactoglobulin (β-Lg) interact to form a к-C/β-Lg complex (A4) apparently composed of three molecules of β-Lg and one molecule of к-C. In a freshly dispersed equimolar mixture of native к-C and β-Lg maintained at 25 °C in 20 mM imidazole at pH 6.8, approximately 14% occurred as a к-C/β-Lg A4complex which increased to about 40% when 20 mM ethylene glycol bis(2-aminoethoxy)-N,N,NʹNʹ-tetraacetic acid (EGTA) was added. The EGTA apparently caused a structural change that resulted in a β-Lg complex (A3) that was highly reactive with monomeric к-C. This reactivity was quenched in the presence of 2.3 M urea. With time, this A4complex became stabilized by covalent bonds. Heating at 70 °C increased the rate of formation of the covalently bonded к-C/β-Lg complex. A possible mechanism for the interaction of к-C with β-Lg involves the formation of a β-Lg homotrimer (A3) complex via hydrophobic interactions that interacts with a к-C molecule.
|Number of pages||6|
|Journal||Journal of Agricultural and Food Chemistry|
|Publication status||Published - 1 Sept 1987|