Comparative cross- linking activities of lactose- specific plant and animal lectins and a natural lactose- binding immunoglobulin G fraction from human serum

Journal/Book: Glycobiology 6 (8), 843-849. 1996;

Abstract: Plant and animal lectins bind and cross-link certain multiantennaryoligosaccharides, glycopeptides, and glycoproteins. This can lead to theformation of homogeneous cross-linked complexes, which may differ intheir stoichiometry depending on the nature of the sugar receptorinvolved. As a precisely defined ligand, we have employed bovineasialofetuin (ASF), a glycoprotein that possesses threeasparagine-linked triantennary complex carbohydrate chains with terminalLacNAc residues. In the present study, we have compared the carbohydratecross-linking properties of two Lac-specific plant lectins, an animallectin and a naturally occurring Lac-binding polyclonal immunoglobulin Gsubfraction from human serum with the ligand. Quantitative precipitationstudies of the Lac-specific plant lectins, Viscum album agglutinin andRicinus communis agglutinin, and the Lac-specific 16 kDa dimericgalectin from chicken liver demonstrate that these lectins formspecific, stoichiometric cross-linked complexes with ASF. At lowconcentrations of ASF, 1:9 ASF/lectin (monomer) complexes formed withboth plant lectins and the chicken lectin. With increasingconcentrations of ASF, 1:3 ASF/lectin (monomer) complexes formed withthe lectins irrespective of their source or size. The naturallyoccurring polyclonal antibodies, however, revealed a differentcross-linking behavior. They show the formation of 1:3 ASF/antibody (perFab moiety) cross-linked complexes at all concentrations of ASF. Thesestudies demonstrate that Lac-specific plant and animal lectins as wellas the Lac-binding immunoglobulin subfraction from specificstoichiometric cross-linked complexes with ASF. These results arediscussed in terms of the structure-function properties of multivalentlectins and antibodies. Author.

Keyword(s): ALPHA-FETOPROTEINS/ ME (metabolism)

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