Glycoprotein allergens in pollen of timothy. IV. Structural studies of a basic glycoprotein allergen

Heat treatment of the glycoprotein allergen with alkaline tritiated borohydride released carbohydrate material in the molecular weight (MW) range 500-2,000 daltons. The radioactivity of the highest MW carbohydrate fraction was low, indicating the presence of alkali-stable hydroxyproline-arabinose linkages. N-acetylglucosaminitol containing 3H was detected in the hydrolysate of the low-MW carbohydrate, indicating that some of the carbohydrate is bound to the protein chain through a N-glycosidic linkage between N-acetylglucosamine and asparagine. The presence of this linkage was also suggested by fast atom bombardment mass spectrometry of pronase-digested allergen. The glycoprotein seems to contain only a few carbohydrate chains made up of a total of 25 monosaccharide units. Methylation analysis indicated that the carbohydrate moiety consists of galactopyranosyl units as branching points linked through 1,3,6-positions or as terminal galactopyranosyl residues, mannopyranosyl groups as part of the chain either as 1,3- or 1,4-linked units, and arabinofuranosyl groups as branching points linked through 1,3,5-positions or as part of the chain, either as 1,3- or 1,5-linked units or as terminal arabinofuranosyl residues.