Primary structure of bovine alpha S1 casein. Partial sequence

Abstract

Earlier work in this laboratory on the determination of the primary structure of bovine αs1 casein [1–5] established that this phosphoprotein is composed of only one single peptide chain of 198 residues. The sequence of 101 residues have already been determined: the substitution of Glu/Gly at position 191 in the COOH‐terminal region differentiates the B and C genetic variants [1–3]. The sequence of 53 amino acid residues in the NH2‐terminal region was also determined [5].This publication deals with the sequence of the central part of the chain. Sequence determinations have been made on various tryptic [2], CNBr and chymotryptic [4] peptides obtained earlier, which have been further broken down with the help of endopeptidases or mild acid hydrolylysis into smaller fragments to which classical methods of degradation have been applied: exopeptidase hydrolysis and substractive Edman's degradation.The results obtained and previously published results establish the sequence of 172 amino acid residues in the molecule. The residues of which the positions have not been established so far are situated in 2 regions of the chain, between position 46 to 52 and position 61 to 77. These 2 regions are characterized by the presence of phosphorus and their sequences will be dealt with in our final publication.