ROLE OF GLYCOSYLATION SITES IN THE IGE FC MOLECULE

The Fc region of immunoglobulin E (IgE) comprising the C(epsilon)3 and C(epsilon)4 domains (residues 329-547) is sufficient for binding to t he high-affinity IgE Fe receptor (Fc epsilon RI alpha). Three potentia l N-linked glycosylation sites are present within the C(epsilon)3 doma in. To determine the effect of the glycosylation sites on IgE Fe synth esis and on Fc epsilon RI alpha binding, site-directed mutagenesis was performed. Mutant IgE Fc constructs were expressed in COS cells and a nalyzed for protein synthesis and secretion, and Fc epsilon RI alpha b inding activity We find that only N-371 and N-394 are glycosylated, an d that the residues surrounding the glycosylation site at N-394 are re quired for Fc epsilon RI alpha binding activity.