Identification of an Epitope Recognized by the Monoclonal Antibody PEP80 in the C-Terminal Cytoplasmic Fragment of Glycophorin A

The monoclonal antibody PEP80 (IgG1) was raised by immunization of BALB/c mice with asialo-agalacto-glycophorin from human erythrocytes. The antibody is specific for glycophorin A (GPA) and reacts strongly with the GPA-derived tryptic peptide which is the C-terminal cytoplasmic portion of GPA, containing amino acid residues 102-131. Using the smaller chymotryptic fragments of this peptide and a set of solid phase-synthesized peptides allowed to establish that the MAb PEP80 is directed against an epitope comprising amino acid residues 112-121 of GPA. The peptides terminated with 120th or 119th amino acid residue were slightly less active, and the minimal structure which still gave a weak reaction with the antibody was the sequence of amino acid residues 112-118. The MAb PEP80 did not bind to live human erythroleukemic K562 cells, but showed a strong binding to the cells permeabilized with methanol.