Identification of the κ-Casein Among the Components of Whole Goat Casein

Abstract Goat κ -casein in the reduced state, probably the natural state, has a mobility on acrylamide gel electrophoresis at pH 9, very close to that of the β -caseins. The goat κ -casein was identified by clotting with rennin, by specific changes in the electrophoretic pattern after rennin action, and by nonprecipitation with calcium ions. It stabilized goat α s -casein so that α s -casein was not precipitated with calcium ions. Polyacrylamide gel electrophoresis of goat κ -casein in some cases gave a single band (together with identifiable contaminants), and, in other cases, gave a multiplicity of slower-moving bands. In all cases only a single major band was observed when the κ -casein was reduced with mercaptoethanol. Components with the mobilities of para- κ -casein were present in considerable amounts in some preparations of κ -casein.