Proteins destined to circulate in the blood are first folded and assembled in the endoplasmic
reticulum of secretory cells. For antibodies, like many other serum proteins, the folding and
assembly steps involve the formation of disulfide bonds. Such bonds have been thought to
be static features of proteins, stabilizing domains, and linking polypeptide chains, although
some cases of extracellular disulfide bond cleavage have been noted. Recently, the human
IgG2 antibody subclass was found to possess multiple structures differing in specific …