Genetic Polymorphism in Caseins of Cow's Milk. V. End-Group Analysis of β-Caseins A, B, and C

Abstract
The 3 known genetic variants of [beta]-casein (A, B, and C) were purified by column chromatography in 3.3 [image] urea, and their purity verified by polyacrylamide-gel electrophoresis. Qualitative determination of the amino-terminal amino-acid by 2 chemical methods revealed arginine for each of the 3 variants. Valine was released most rapidly and closely followed by isoleucine during reaction with carboxypeptidase-A. The data indicate either an ileu-ileu-val or an ileu-val-ileu C-terminal sequence in each variant. Molecular weight of about 25,000 for the [beta]-caseins (A, B and C) were calculated from the amount of valine released.