DIFFERENCES IN THE CROSS-LINKING ACTIVITIES OF NATIVE AND RECOMBINANT ERYTHRINA CORALLODENDRON LECTIN WITH ASIALOFETUIN - EVIDENCE FOR CARBOHYDRATE-CARBOHYDRATE INTERACTIONS IN LECTIN-GLYCOPROTEIN COMPLEXES

A previous study showed that several multivalent galactose-specific lectins including the 14-kDa lectin from calf spleen and the lectins from Erythrina indica, Erythrina cristagalli, and soybean agglutinin formed specific cross-linked complexes with the glycoprotein asialofetuin (ASF) [Mandal, D. K., and Brewer, C. F. (1992) Biochemistry 31, 8465-8472]. In the present study, we have used quantitative precipitation analysis to compare the cross-linking activities of the Gal/GalNAc-specific lectin from Erythrina corallodendron (ECorL) and the recombinant protein (rECorL) which lacks the covalently linked heptasaccharide chains of the native lectin, with ASF. At low concentrations of ASF relative to the lectin, native dimeric ECorL binds to each of the three terminal Gal residues of the three N-linked triantennary chains of ASF and precipitates as a cross-linked complex at a ratio of 1:9 ASF/lectin (monomer). With increasing concentrations of ASF, the 1:9 complex changes to a 1:3 ASF/lectin complex, and at higher ASF concentrations, a 1:1 cross-linked complex forms. However, rECorL, which possesses the same specificity and binding affinity as the native lectin, forms only the 1:9 and 1:3 ASF/lectin complexes. Other Erythrina lectins examined, all of which have covalently attached carbohydrate and are structurally similar to ECorL, show the same cross-linking behavior as native ECorL. On the other hand, the dimeric 14-kDa calf spleen lectin which lacks covalently attached carbohydrate forms only 1:9 and 1:3 cross-linked complexes with ASF [Mandal, D. K., and Brewer, C. F. (1992) Biochemistry 31, 8465-8472]. SBA, which is a tetrameric lectin with one Man9 oligomannose chain per monomer, formed 1:3 and 1:2 ASF/lectin (monomer) crosslinking complexes. Peanut agglutinin, which is a tetrameric Gal-specific lectin lacking covalently linked carbohydrate, formed only a 1:3 ASF/lectin cross-linked complex. These results indicate that lectins with covalently attached carbohydrates form specific ASF/lectin cross-linked complexes which are not formed by nonglycosylated lectins. This suggests that interactions occur between the carbohydrate chains of the glycoprotein lectins and the carbohydrate chains of ASF which stabilize the formation of certain ASF/lectin cross-linked complexes.