CARBOHYDRATE CHARACTERIZATION OF PURIFIED THYROXINE-BINDING GLOBULIN BY LECTIN BLOT AND ISOELECTRIC FOCUSING

Summary: The structure of carbohydrate moiety of purified thyroxine-binding globulin (TBG) was examined by lectin blot and isoelectric focusing (IEF). In lectin blot, TBG reacted positively with the following lectins: Sambucus nigra agglutinin (SNA I), Ricinus communis agglutinin (RCA I), wheat germ lectin (WGA), phytoheamagglutinin (PHA) and pea lectin (PSA). The obtained results indicate that purified TBG contains N-linked oligosaccharide chains consisting of mannose, galactose, N-acetylglucosamine and sialic acid. Isoelectric focusing of TBG at pI 4.2’ 4.6 revealed three bands, which confirmed that isolated TBG had retained its structure without desialylation. Lectin blot analysis and IEF can be considered to be useful tools in the study of TBG glycosylation.