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

A previous study showed that several multivalent galactose-specific le ctins including the 14-kDa lectin from calf spleen and the lectins fro m Erythrina indica, Erythrina cristagalli, and soybean agglutinin form ed specific cross-linked complexes with the glycoprotein asialofetuin (ASF) [Mandal, D. K., and Brewer, C. F. (1992) Biochemistry 31, 8465-8 472]. In the present study, we have used quantitative precipitation an alysis to compare the cross-linking activities of the Gal/GalNAc-speci fic lectin from Erythrina corallodendron (ECorL) and the recombinant p rotein (rECorL) which lacks the covalently linked heptasaccharide chai ns of the native lectin, with ASF. At low concentrations of ASF relati ve to the lectin, native dimeric ECorL binds to each of the three term inal 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 chang es to a 1:3 ASF/lectin complex, and at higher ASF concentrations, a 1: 1 cross-linked complex forms. However, rECorL, which possesses the sam e specificity and binding affinity as the native lectin, forms only th e 1:9 and 1:3 ASF/lectin complexes. Other Erythrina lectins examined, all of which have covalently attached carbohydrate and are structurall y similar to ECorL, show the same cross-linking behavior as native ECo rL. On the other hand, the dimeric 14-kDa calf spleen lectin which lac ks covalently attached carbohydrate forms only 1:9 and 1:3 cross-linke d complexes with ASF [Mandal, D. K., and Brewer, C. F. (1992) Biochemi stry 31, 8465-8472]. SBA, which is a tetrameric lectin with one Man9 o ligomannose 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 lecti ns with covalently attached carbohydrates form specific ASF/lectin cro ss-linked complexes which are not formed by nonglycosylated lectins. T his suggests that interactions occur between the carbohydrate chains o f the glycoprotein lectins and the carbohydrate chains of ASF which st abilize the formation of certain ASF/lectin cross-linked complexes.