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Title
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Investigation of the interaction between the class I MHC-related Fc receptor and its immunoglobulin G ligand.
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Authors
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M.Raghavan,
M.Y.Chen,
L.N.Gastinel,
P.J.Bjorkman.
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Ref.
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Immunity, 1994,
1,
303-315.
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PubMed id
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Abstract
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The neonatal Fc receptor (FcRn) is structurally similar to class I major
histocompatibility molecules. FcRn transports maternal immunoglobulin G (IgG)
from ingested milk into the blood. IgG is bound at the pH of milk (pH 6.0-6.5)
in the gut and released at the pH of blood (pH 7.5). We find that alteration of
a histidine pair within the alpha 3 domain of FcRn and of a nearby loop (the
FcRn counterpart of the class I CD8-binding loop) affects the affinity for IgG.
Inhibition studies suggest the involvement of the FcRn B2-microglobulin domain
in IgG binding. Fragment B of protein A inhibits FcRn binding to IgG, localizing
the binding site on Fc for FcRn to the CH2-CH3 domain interface. Three
histidines present at the CH2-CH3 domain interface of Fc could be partially
responsible for the pH-dependent interaction between FcRn and IgG.
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