151. Identification of the high affinity receptor binding region in human immunoglobulin E.
- Author
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Helm BA, Sayers I, Higginbottom A, Machado DC, Ling Y, Ahmad K, Padlan EA, and Wilson AP
- Subjects
- Animals, Base Sequence, Binding Sites, Cell Line, Cloning, Molecular, DNA Primers, Escherichia coli, Glutathione Transferase biosynthesis, Humans, Hydrogen-Ion Concentration, Immunoglobulin Fab Fragments chemistry, Immunoglobulin epsilon-Chains biosynthesis, Models, Molecular, Molecular Sequence Data, Mutagenesis, Mutagenesis, Site-Directed, Point Mutation, Polymerase Chain Reaction, Rats, Receptors, IgE biosynthesis, Receptors, IgG metabolism, Recombinant Fusion Proteins biosynthesis, Recombinant Fusion Proteins chemistry, Recombinant Fusion Proteins metabolism, Restriction Mapping, Sequence Deletion, Immunoglobulin E chemistry, Immunoglobulin E metabolism, Immunoglobulin epsilon-Chains chemistry, Immunoglobulin epsilon-Chains metabolism, Protein Conformation, Receptors, IgE metabolism
- Abstract
We have investigated the capacity of N- and C-terminally truncated and chimeric human (h) IgE-derived peptides to inhibit the binding of 125I-labeled hIgE, and to engage cell lines expressing high and low affinity receptors (Fc-epsilon-RI/II). The peptide sequence Pro343-Ser353 of the hC-epsilon-3 domain is common to all h-epsilon-chain peptides that recognize hFc-epsilon-RI. This region in IgE is homologous to the A loop in C-gamma-2 that engages the rat neonatal IgG receptor. Optimum Fc-epsilon-RI occupancy by hIgE occurs at pH 6.4, with a second peak at 7.4. N- or C-terminal truncation has little effect on the association rate of the ligands with this receptor. Dissociation markedly increases following C-terminal deletion, and hFc-epsilon-RI occupancy at pH 6.4 is diminished. His residue(s) in the C-terminal region of the epsilon-chain may thus contribute to the high affinity of interaction. Grafting the homologus rat epsilon-chain sequence into hIgE maintains hFc-epsilon-RI interaction without conferring binding to rat Fc-epsilon-RI. hFc-epsilon-RII interaction is lost, suggesting that these residues also contribute to hFc-epsilon RII binding. h-epsilon-chain peptides comprising only this sequence do not block hIgE/hFc-epsilon-RI interaction or engage the receptor. Therefore, sequences N- or C-terminal to this core peptide provide structures necessary for receptor recognition.
- Published
- 1996
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