Figure 1.

Interaction between the FcRn and IgG. The FcRn is composed of a heavy chain with three extracellular domains (α1, α2, α3, dark blue) and of the β-2 microglobulin light chain (β2 m, light blue). At acidic pH, salt bridges are formed upon interactions between the histidine residues His310, His435, and His436 of the CH2 and CH3 domains of the IgG and glutamate residues Glu117 and Glu132 of the α2 domain of the heavy chain of FcRn, and the isoleucine residue Ile1 of the β 2 m. The IgG is depicted in orange.