The neonatal Fc receptor (FcRn) transports maternal immunoglobulin G (IgG) to the bloodstream of the newborn. FcRn is structurally similar to class I major histocompatibility complex (MHC) molecules, despite differences in the ligands they bind (the Fc portion of IgG and antigenic peptides, respectively) ...
The neonatal Fc receptor (FcRn) transports maternal immunoglobulin G (IgG) to the bloodstream of the newborn. FcRn is structurally similar to class I major histocompatibility complex (MHC) molecules, despite differences in the ligands they bind (the Fc portion of IgG and antigenic peptides, respectively). A low-resolution crystal structure of the complex between FcRn and Fc localizes the binding site for Fc to the side of FcRn, distinct from the tops of the alpha 1 and alpha 2 domains which serve as the peptide and T-cell receptor binding sites in class I molecules. FcRn binds to Fc at the interface between the Fc CH2 and CH3 domains, which contains several histidine residues that could account for the sharply pH-dependent FcRn/IgG interaction. A dimer of FcRn heterodimers observed in the co-crystals and in the crystals of FcRn alone could be involved in binding Fc, correlating with the 2:1 binding stoichiometry between FcRn and IgG (ref. 4) and suggesting an unusual orientation of FcRn on the membrane.
Related Citations:
Crystal Structure at 2.2 Angstroms Resolution of the Mhc-Related Neonatal Fc Receptor Burmeister, W.P., Gastinel, L.N., Simister, N.E., Blum, M.L., Bjorkman, P.J. (1994) Nature 372: 336
Investigation of the Interaction between the Class I Mhc-Related Fc Receptor and its Immunoglobulin G Ligand Raghavan, M., Chen, M.Y., Gastinel, L.N., Bjorkman, P.J. (1994) Immunity 1: 303
Crystallization and Stoichiometry of Binding of a Complex between a Rat Intestinal Fc Receptor and Fc Huber, A.H., Kelly, R.F., Gastinel, L.N., Bjorkman, P.J. (1993) J Mol Biol 230: 1077
Crystallographic Refinement and Atomic Models of a Human Fc Fragment and its Complex with Fragment B of Protein a from Staphylococcus Aureus at 2.9-And 2.8-Angstroms Resolution Deisenhofer, J. (1981) Biochemistry 20: 2361
Organizational Affiliation:
Division of Biology 156-29, California Institute of Technology, Pasadena 91125.
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