OBSERVATION OF UNIQUE CROSS-LINKED LATTICES BETWEEN MULTIANTENNARY CARBOHYDRATES AND SOYBEAN LECTIN - PRESENCE OF PSEUDO-2-FOLD AXES OF SYMMETRY IN COMPLEX TYPE CARBOHYDRATES

The tetrameric lectin from Glycine max (soybean) (SBA) has been shown to cross-link and precipitate with N-linked multiantennary complex typ e oligosaccharides containing nonreducing terminal Gal residues (Bhatt acharyya, L., Haraldsson, M., and Brewer, C.F. (1988) Biochemistry 27, 1034-1041). In the present study, negative stain electron micrographs of the precipitates of SBA with a series of naturally occurring and s ynthetic multiantennary carbohydrates with terminal Gal or GalNAc resi dues show the presence of highly ordered cross-linked lattices for man y of the complexes. The precipitates of SBA with a ''bisected'' and '' nonbisected'' N-linked biantennary complex type oligosaccharide contai ning Gal residues at the nonreducing termini show similar two-dimensio nal patterns. However, the pattern observed for the precipitates of a tetraantennary complex type oligosaccharide with SBA is distinct from those of the two biantennary carbohydrates. Furthermore, the precipita tes formed between the lectin and a synthetic O-linked biantennary ('' cluster'') glycoside with terminal GalNAc residues show a pattern that is different from those above. Four biantennary pentasaccharide analo gs of the blood group I antigen containing beta-LacNAc moieties at the 2,3-, 2,4-, 2,6-, and 3,6-positions of the core Gal also showed order ed patterns in their precipitates with SBA. X-ray crystallographic dat a and mixed quantitative precipitation profiles of binary mixtures of the four analogs demonstrate that each analog possesses a unique cross -linked lattice with the protein. A common structural feature of the n aturally occurring and synthetic 'carbohydrates that show highly organ ized cross-linked lattices with SBA is the presence of a pseudo-2-fold axis of symmetry in each oligosaccharide relating the terminal bindin g epitopes on each arm. This suggests that the symmetry features of ce rtain naturally occurring branch chain oligosaccharides facilitate for mation of highly ordered, homogeneous cross-linked complexes with spec ific lectins.