Figure 6.

Both the cytokinergic IgE SPE-7 and the autoantibody RF-AN use similar protein surfaces to mediate cross-reactive protein-protein interactions. (A) Crystal structure of SPE-7 IgE bound to a phage display selected mutant thioredoxin (pdb: 1OAZ). The major SPE-7 IgE conformer (Ab¹) binds to the thioredoxin to form the Ab⁴-thioredoxin complex (James et al., 2003). (B) Crystal structure of the IgM autoantibody RF-AN bound to the IgG₄ Fc domain (pdb: 1ADQ; Corper et al., 1997). For clarity only the proteins within the asymmetric unit of the crystal and the Fv region of RF-AN are shown.