Structural studies on allergen RC-13 from Ricinus communis L.: isolation and characterization of a major glycopeptide

A glycoprotein, RC-13, isolated from Ricinus communis seeds was reduced, S-alkylated and cleaved by trypsin. The tryptic digest was fractionated by ion-exchange chromatography and a glycopeptide was isolated and purified by high-voltage paper electrophoresis. When submitted to amino acid and carbohydrate analyses this major glycopeptide showed the following chemical composition: Lys1, Asp1, Thr2, Ser4, Glu1, Pro2, Gly2, Ala2, Val2, GlcN6, Man6 and Gal8. Hydrazynolysis positioned Ser as the C-terminal residue. It is postulated that this glycopeptide belongs to the C-terminal region of the allergen