Interactions of concanavalin A with glycoproteins: formation of homogeneous glycoprotein-lectin cross-linked complexes in mixed precipitation systems.

We have previously demonstrated that the interactions between branched chain oligosaccharides and glycopeptides isolated from glycoproteins and glycolipids with specific lectins lead to the formation of homopolymeric carbohydrate-protein cross-linked complexes, even in the presence of mixtures of the carbohydrates or lectins cf. Bhattacharyya, L., Fant, J., Lonn, H., & Brewer, C. F. (1990) Biochemistry 29, 7523-7530]. Recently, we have shown that highly ordered cross-linked lattices are formed between the tetrameric glycoprotein soybean agglutinin (SBA), which possesses a Man9 oligomannose chain per monomer, and the Glc/Man-specific plant lectin concanavalin A (Con A) Khan, M. I., Mandal, D. K., & Brewer, C. F. (1991) Carbohydr. Res. 213, 69-77]. Using radiolabeling and quantitative precipitation techniques, we show in the present study that Con A binds and forms unique cross-linked complexes with four different glycoproteins having different numbers and types of carbohydrate chains as well as different quaternary structures. The glycoproteins include quail ovalbumin, Lotus tetragonolobus isolectin A (LTL-A), Erythrina cristagalli lectin (ECL), and Erythrina corallodendron lectin (EcorL). The results show that a preparation of quail ovalbumin containing either one Man7 or Man8 oligomannose chain per molecule forms a 1:2 cross-linked complex with tetrameric Con A, thereby demonstrating bivalency of the single carbohydrate chain(s) on the glycoprotein. Tetrameric LTL-A and dimeric ECL, which possess two xylose-containing carbohydrate chains per monomer, both form 1:2 and 1:1 cross-linked complexes (per monomer) of glycoprotein to lectin, depending on their relative ratios in solution. However, dimeric EcorL, which has the same carbohydrate structure and number of chains as ECL, forms only a 1:2 cross-linked complex with tetrameric Con A.(ABSTRACT TRUNCATED AT 250 WORDS)