The glycoprotein allergen Ag-54 (Cla h II) from Cladosporium herbarum. Structural studies of the carbohydrate moiety

Abstract

The carbohydrate moiety of an important allergen, Ag-54 in Cladosporium herbarum was studied by alkaline-borohydride treatment, gel filtration, high-performance liquid chromatography, methylation analysis, gas liquid chromatography and mass spectometry. The Ag-54 protein core possessed a very limited number of sugar chains. The carbohydrate moiety consisted mainly of one large highly branched polysaccharide chain which accounted for nearly 75% of the total molecular weight of the glycoprotein. The carbohydrate moiety is made up of D-mannose and D-glucose units in pyranose form having D-galactofuranose side chains attached. Mannose is both 1,2- and 1,6-linked, while glucose is 1,4- and 1,6-linked. Some of the 1,6-linked galactofuranose side chains are bound through C-2 of the 1,6-linked mannose units, and the rest to C-3 of 1,6-linked mannose and 1,2-linked mannose units. A few oligoglucosidic chains of approximately 4 glucose units are also attached to the protein.