Crystal state and solution conformation of the B blood group trisaccharide α‐l‐Fucp‐(1→2)‐[α‐d‐Galp]‐(1→3)]‐β‐d‐Galp‐OCH₃

Abstract

Crystal state and solution conformation of the B blood group trisaccharide a-l l-Fucp-(132)-[a-d d-Galp]-(133)]-b-d d-Galp-OCH 3Albin Otter, Raymond U. Lemieux, Richard G. Ball, Andre  P. Venot, Ole Hindsgaul and David R. Bundle Department of Chemistry, University of Alberta, Edmonton, CanadaThe crystal structure of the human B blood group related trisaccharide a-l-Fucp-(132)-[a-d-Galp]-(133)-b-dGalp-OCH 3 (1) has been determined. The solution structure of 1 was studied by two-dimensional NMR techniques at 600 MHz in D 2 O solution and the conformational properties were analyzed in terms of the torsional angles f H and c H , derived from 3 J CH coupling constants, and 10 inter-residue proton±proton distances. 3 J CH could be accurately measured by a recently introduced two-dimensional heteronuclear correlation experiment (EXSIDE). The nuclear Overhauser enhancement-derived distances and the calculated torsion angles were compared with the same information available from the crystal structure. The agreement is excellent, indicating that the trisaccharide adopts a restricted conformation in solution, which was also predicted by the Hard Sphere Exo-Anomeric forcefield. The data of 1 are complemented by NMR studies of the closely related a-l-Fucp- (132)Keywords: B blood group antigenic determinant; carbon-proton long-range coupling constants; conformation in solution and in the crystal; torsional angles; X-ray crystallography.The human A and B blood group antigenic determinants are the major isoantigens of importance to blood transfusion and tissue transplantation. The conformation of the B blood group trisac- (Fig. 1) was concluded to be relatively rigid, first by Lemieux et al. [1,2] and later confirmed in various solvents for closely related molecules by Bush et al. [3,4]. There has been debate as to what extent oligosaccharides in general can be treated as substantially rigid molecules [5,6]. Their conformational properties have therefore been extensively probed by both theoretical and experimental methodologies. The latter are in general restricted to NMR studies in solution but the inherent time-averaging of the inter-proton distances always poses a problem [7]. Crystallography can provide a firm indication of a conformational preference but only relatively limited information is available for oligosaccharides in the crystalline form, primarily because many of the oligosaccharides of interest have resisted attempts to form useful crystals.In this work, we report the crystal structure of the human blood group trisaccharide 1. We also describe conformational studies performed on 1. It was previously noted that the glycosidic torsional angles deduced from preliminary crystal structure data agreed with calculation and NMR experiments [8]. The details of the crystal structure are reported here in conjunction with a thorough examination of its conformational preference in D 2 O solution using modern NMR techniques at 600 MHz.Despite the limited instrumentation available 20 years ago, evidence was obtained, that the...

Conformational studies of blood group A and blood group B oligosaccharides using NMR residual dipolar couplings

“…7. These models are conformationally very similar and agree very well with the conformations reported for blood group B by Otter et al 7 and with the model initially proposed for solution by Bush et al 2 and obtained later by Casset et al complexed with a lectin 6 specific for blood group A.…”

“…Also, the reported long-range couplings 3 J CH on blood group B are consistent only with the family I. 7 Additional calculations were done with the TRAMITE method to evaluate the possibility of flexible conformations for the blood group epitopes. In these calculations, a series of ensembles composed of conformers selected in order of increasing energy and having values below 3, 4, and 5 were used to predict the 1 D CH values.…”

“…5 New experimental studies of blood group A based on NMR relaxation measurements reported agreement with the two conformer model, 6 but later reports on blood group B using NMR long-range coupling constants concluded the presence of just one conformer. 7 Residual dipolar couplings (RDC) measured in oriented media 8 provide a relatively new technique that is having a high impact in structure determinations of proteins and oligosaccharides. In general they are easy to measure with high accuracy, and they give important structural and dynamic information.…”

The Unique Solution Structure and Immunochemistry of theCandida albicans β-1,2-Mannopyranan Cell Wall Antigens

“…This occurs for well defined oligosaccharide conformations that most often result from branching through vicinal substitution, as is the case with the blood group A and B antigens. In this and other such structures (45)(46)(47), NOE contacts between non-contiguous residues (for example n and n ϩ 2) often occur spanning the branched pyranose ring. A linear homopolysaccharide can achieve the equivalent of vicinal substitution only if the hydroxyl group adjacent to the anomeric center is the site for chain extension.…”

Activity–structure correlations in divergent lectin evolution: fine specificity of chicken galectin CG-14 and computational analysis of flexible ligand docking for CG-14 and the closely related CG-16

“…They were previously described by molecular mechanics calculations and NMR spectroscopy (Yan and Bush, 1990;Imberty et al 1995;Koca et al 1995;Casset et al 1996;Otter et al 1999; Azurmendi and Bush, …”