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Figure 1.
Domain structure of SIgA2. SIgA2 is shown as two IgA2m(1)
monomers, a J chain, and a secretory component (domains
D1–D5). Each IgA2 heavy chain contains the V[H], C[H]1, C[H]2,
and C[H]3 domains. Each light chain contains the V[L] and C[L]
domains. The complementarity-determining regions (CDR), the
13-residue hinge and the 18-residue C-terminal tailpiece are
highlighted. The IgA2m(2) allotype does not have a
Cys^214–Cys^214 disulfide bridge. The possible interheavy
chain disulfide bridges at Cys^241, Cys^242, Cys^299, and
Cys^301 are denoted by an extended X. Cys^471 in one tailpiece
of each Fc region is disulfide-bridged with either Cys^15 or
Cys^68 in the J chain, which is located on the convex edge of
the Fc-Fc region. A Cys^311–Cys^502 bridge between the C[H]2
and D5 domains is shown. N-Linked oligosaccharide sites are
denoted by filled symbols (•).
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