Franklin's disease: Ig gamma 2 H chain mutant BUR.

The complete sequence of a gamma 2-H chain disease protein BUR is presented. This mutant, a dimer of a 348-residue chain, linked by four disulfide bridges, is composed of a complete V region, hinge, CH2, and CH3 domains. There is one deletion, the CH1 domain, which includes the cysteine residue bridging the H to L chain. Although the V region is encoded by the VHI and JHIII genes, it has several distinctions: methionine at position 11, two unique cysteine residues in the second complementarity determining region (CDR2), and three glycosylation sites, two of which are located in the CDR2 and CDR3 regions. These distinctive characteristics of BUR VH within the framework of a normal VHI may be affected by extensive somatic mutation or by a rare and previously unanalyzed VH gene.