Localization of two interchain disulfide bridges in dimers of bovine alpha s2-casein. Parallel and antiparallel alignments of the polypeptide chains.
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.
Rasmussen
L K
LK
MD Foods Research and Development Center, Brabrand, Denmark.
Højrup
P
P
Petersen
T E
TE
D000595:Amino Acid Sequence; D000818:Animals; D002364:Caseins / Q000737:chemistry* / Q000378:metabolism; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D002918:Chymotrypsin / Q000737:chemistry; D004220:Disulfides / Q000737:chemistry* / Q000378:metabolism; D005561:Formates / Q000737:chemistry; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010455:Peptides / Q000302:isolation & purification; D014357:Trypsin / Q000737:chemistry
D002364:Caseins; D004220:Disulfides; D005561:Formates; D010455:Peptides; C008817:peroxyformic acid; D002918:Chymotrypsin; D014357:Trypsin