Monosaccharide and oligosaccharide analysis of proteins transferred to polyvinylidene fluoride membranes after sodium dodecyl sulfate-polyacrylamide gel electrophoresis

We have developed an intermediate method toward the complete carbohydrate analysis of proteins, which should be universally applicable to all proteins and independent of sample matrix. Using only Coomassie Blue-stained proteins which have been electroblotted onto polyvinylidene fluoride membranes, we report a strategy for: (i) determining unequivocally whether a protein is glycosylated; (ii) obtaining a complete monosaccharide composition; (iii) oligosaccharide mapping which separates most forms according to size, charge and isomerity; and (iv) sequentially releasing and analyzing specific classes of oligosaccharides with endoglycosidases. The method was shown to be applicable to a variety of well characterized soluble glycoproteins and to the membrane-bound protein, the gastric H⁺,K⁺-ATPase. The monosaccharide composition of the H⁺,K⁺-ATPase revealed the absence of N-acetylneuraminic or N-glycolylneuraminic acids and a monosaccharide composition which indicated O-linked sugar chains. Oligomannosidic/hybrid and biantennary oligosaccharides were sequentially released and analyzed from one electroblotted band of recombinant tissue plasminogen activator using endo-β-AT-acetylglucosaminidase H and endo-β-AT-acetylglucosaminidase F2, respectively. Sialylated polylactosamine structures were identified and quantified by analyzing high performance liquid chromatography profiles of oligosaccharides first released by peptide-N⁴-(N-acetyl-β-D-glucosaminyl)asparagine amidase and then treated with endo-β-galactosidase, using a single, stained band of recombinant erythropoietin. This recombinant erythropoietin was found to contain eight times more tetrasialylated oligosaccharides than previously reported (Sasaki, H., Bothner, B., Dell, A., and Fukuda, M. (1987) J. Biol. Chem. 262, 12059-12076); 47% of released oligosaccharides were identified as polylactosamine structures.