Structural analysis of the peptides derived from specific acid-catalyzed hydrolysis at aspartylprolyl peptide bonds in human J chain.

Human J chain from IgM has been selectively cleaved at three aspartylprolyl peptide bonds to yield four fragments containing 62, 20, 25, and 22 amino acids, respectively. The amino acid sequence of each peptide has been partially determined, (59 of a total of 129 residues) and its position in the J chain ascertained. There were no obvious similarities to known sequences in other immunoglobulin polypeptide chains.