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

Abstract

Goat k-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 [beta]-caseins. The goat k-casein was identified by clotting with rennin, specific changes in the electrophoretic pattern after rennin action and nonprecipitation with Ca ions. It stabilized goat [alpha]s-casein so that [alpha]s-casein was not precipitated with Ca ions. Polyacrylamide gel electrophoresis of goat k-casein gave a single band (together with identifiable contaminants) in some cases and a multiplicity of slower-moving bands in other cases. Only a single major band was observed when the k-casein was reduced with mercapto-ethanol in all cases. Components with the mobilities of para-k-casein were present in considerable amounts in some preparations.