Solubilization and partial characterization of a phytohemagglutinin receptor site from human erythrocytes.

Trypsin treatment of human erythrocytes releases a soluble glycopeptide which binds to phytohemagglutinin and abolishes the erythroagglutinating and lymphocyte-stimulating properties of this molecule. The glycopeptide has been purified by alkaline borohydride treatment, proteolytic digestion, gel filtration, and DEAE-cellulose chromatography. The most highly purified glycopeptide has a molecular weight of about 2,000. The specificity for binding to phytohemagglutinin resides in the oligosaccharide portion of the molecule with the determinant sugar being a galactose residue which is penultimate to a N-acetylneuraminic acid in some chains and uncovered in others. The glycopeptide is about 3,000 times more potent than either N-acetylgalactosamine or galactose in inhibiting the mitogenic response of lymphocytes induced by phytohemagglutinin.