Identification of a linear epitope for Fc-binding in the mouse FcγRIII

Fc receptors are transmembrane proteins, found on the surfaces of immune cells, that aid in the removal of foreign pathogens by binding to antibody-coated targets via the Fc regions of the antibodies. To identify sites on mouse FcγRIII (moFcγRIII) α-chain that bind to the Fc region, peptides derived from the proximal extracellular domain (EC2) of moFcγRIII α-chain corresponding to the homologous region of human FcγRIIIB α-chain were synthesized. Binding of mouse IgG to the different peptides was tested by Dot-blot assay. The effective peptide 119SFFHNEKSVRYH130 located in the putative C–C′ loop of the EC2 domain was found to bind mouse IgG specifically with an affinity of approximately 5.58 × 10−5 M and inhibit the binding of mouse IgG to the receptor. Such a functional peptide should be very useful for further understanding the IgG–FcγR interaction and development of FcR-targeting drugs.