Data bank of three-dimensional structures of disaccharides: Part II, N-acetyllactosaminic type N-glycans. Comparison with the crystal structure of a biantennary octasaccharide.

Conformational energy maps and descriptions of structures at the local minima are presented for the following fragments found in N-acetyllactosaminic type glycans of N-glycoproteins: GlcNAc beta(1-2)Man, GlcNAc beta(1-4)Man, GlcNAc beta(1-6)Man, Gal beta(1-4)GlcNAc, GlcNAc beta(1-3)Gal, Fuc alpha(1-6)GlcNAc, Fuc alpha(1-3)GlcNAc, Xyl beta(1-2)Man, Gal beta(1-3)GlcNAc and GlcNAc beta(1-6)Gal. These results are the second part of a data bank on glycoprotein moieties; five disaccharides found in oligomannose type N-glycans were analysed earlier (Imberty et al., 1990, Glycoconjugate J 7:27-54). In the present study, three to seven minima are found for each dimer. Conformations of disaccharide fragments found in the crystal structure of the complex of a biantennary octasaccharide with Lathyrus ochrus lectin are plotted on these energy maps. While the observed conformations are at predicted minima, they are not always at the minimum predicted to have the lowest energy. Further, not all observed conformations are stabilized by the exo-anomeric effect. We conclude that these oligosaccharides are highly flexible.