Identification of the linear epitope for Fc-binding on the bovine IgG2 Fc receptor (boFcγ2R) using synthetic peptides

To identify the linear epitope for Fc-binding on the bovine IgG2 Fc receptor (boFcγ2R), peptides derived from the membrane-distal extracellular domain (EC1) of boFcγ2R corresponding to the homologous region of human FcαRI were synthesized. Binding of bovine IgG2 to the different peptides was tested by Dot-blot assay, and the peptide showing maximal binding was further modified by truncation and mutation. The minimum effective peptide 82FIGV85 located in the putative F–G loop of the EC1 domain was found to bind bovine IgG2 specifically and inhibit the binding of bovine IgG2 to the receptor. The Phe82, Ile83 and Val85 residues within the linear epitope were shown to be critical for IgG2-binding. Such functional epitope peptide should be very useful for understanding the IgG-Fcγ interaction and development of FcR-targeting drugs.