Structure of the hinge region of the mu heavy chain of human IgM immunoglobulins.

The amino acid sequence around the central disulfide bridge linking the mu heavy chains of the human immunoglobulin M monomer is unlike that in immunoglobulin G. This hinge area contains one of the five oligosaccharides of the mu chain, is low in proline, and is the site of tryptic cleavage to yield Fabmicro and Fcmicro fragments.