The molecular defect in a protein (CRA) found in gamma-1 heavy chain disease, and its genetic implications.

A gamma1 protein, designated CRA, found in heavy chain disease contains three inter-heavy disulfide bridges instead of the two normally found in gamma1 immunoglobulin heavy chains. Almost the entire Fd fragment is missing. The NH(2) terminal region is heterogeneous and contains carbohydrate; after 11 residues that do not resemble any of the known heavy-chain variable-region subclasses, normal synthesis seems to be resumed at the same amino acid residue as in another heavy-chain disease protein (ZUC). This finding raises the possibility that glutamic acid at position 216 represents the beginning of the Fe region, synthesized under the direction of another gene.