Complete amino acid sequence of a mouse mu chain: homology among heavy chain constant region domains.

The complete amino acid sequence of the mouse mu chain secreted by the MOPC 104E myeloma tumor has been determined. There are four constant region domains in the mu chain and a 20-residue COOH-terminal segment that plays a role in the polymerization of pentameric immunoglobulin M molecules. There are six sites of carbohydrate attachment in the MOPC 104E mu chain. Three complex-type and two high-mannose oligosaccharides are located in the mu chain constant region. The general type and location of carbohydrate moieties in the mu chain constant region are completely conserved between mouse and human mu chains. Homology in the location of carbohydrate structures on different classes of heavy chains is discussed.