Formation of homogeneous carbohydrate–lectin cross‐linked precipitates from mixtures of D‐galactose/N‐acetyl‐D‐galactosamine‐specific lectins and multiantennary galactosyl carbohydrates

Quantitative precipitation studies have shown that the Man/Glc‐specific lectin concanavalin A (ConA) forms homogeneous (homopolymeric) cross‐linked precipitates with individual asparagine‐linked oligomannose and bisected hybrid‐type glycopeptides in the presence of binary mixtures of the carbohydrates [Bhattacharyya, L., Khan, M. I. & Brewer, C. F. (1988) Biochemistry 27, 8762–8767]. The results indicate that the ConA‐glycopeptide precipitates are highly organized cross‐linked lattices that are unique for each carbohydrate. Using similar techniques, the present study shows that the Gal‐specific lectins from Erythrina indica and Ricinus communis (agglutinin I) form homogeneous cross‐linked complexes with individual carbohydrates in binary mixtures of triantennary and tetraantennary complex‐type oligosaccharides with terminal Gal residues. Conversely, binary mixtures of Gal/GalNAc‐specific lectins from E. indica, Erythrina cristagalli, Erythrina flabelliformis, R. communis, soybean (Glycine max), and Wistaria floribunda (tetramer) in the presence of a naturally occurring or synthetic branched‐chain oligosaccharide with terminal GalNAc or Gal residues provide evidence for the formation of separate cross‐linked lattices between each lectin and the carbohydrate. The present results therefore demonstrate the formation of homogeneous lectin–carbohydrate cross‐linked lattices in (a) a mixture of branched‐chain complex‐type oligosaccharides in the presence of a specific Gal/GalNAc‐binding lectin, and (b) a mixture of lectins with similar physicochemical and carbohydrate binding properties in the presence of an oligosaccharide. These findings show that lectin–carbohydrate cross‐linking interactions provide a high degree of specificity which may be relevant to their biological functions as receptors.