Rasmussen L K, Højrup P, Petersen T E
MD Foods Research and Development Center, Brabrand, Denmark.
Eur J Biochem. 1992 Feb 1;203(3):381-6. doi: 10.1111/j.1432-1033.1992.tb16561.x.
Carboxymethylation of bovine skimmed milk with 14C-labelled iodoacetic acid followed by purification of the alpha s2-casein dimer showed that all four cysteine residues in the protein are engaged in disulfide linkages. Mass spectrometry and sequence analysis of cystine-containing tryptic peptides revealed the presence of two interchain disulfide bridges in the protein. Sequence analysis of disulfide-linked peptides resulting from an enzymatic cleavage between the bridges demonstrated that the individual chains in the dimers are either aligned in an antiparallel or a parallel orientation. The identity of some of the disulfide-linked peptides was further verified by performic acid oxidation followed by sequence analysis of the resulting peptides.
