PDBsum entry 2e51

Sugar binding protein

PDB id: 2e51

Contents

Protein chains

236 a.a. *

Ligands

GLA-A2G ×4

NAG-FUC-NAG ×6

NAG-NAG-BMA-FUC

NAG-NAG

Metals

_CA ×4

_MN ×4

Waters ×268

* Residue conservation analysis

PDB id:

2e51

Name:

Sugar binding protein

Title:

Crystal structure of basic winged bean lectin in complex with a blood group disaccharide

Structure:

Basic agglutinin. Chain: a, b, c, d. Synonym: wba i

Source:

Psophocarpus tetragonolobus. Winged bean. Organism_taxid: 3891

Resolution:

2.50Å R-factor: 0.192 R-free: 0.228

Authors:

K.A.Kulkarni,S.Katiyar,A.Surolia,M.Vijayan,K.Suguna

Key ref:

K.A.Kulkarni et al. (2007). Generation of blood group specificity: new insights from structural studies on the complexes of A- and B-reactive saccharides with basic winged bean agglutinin. Proteins, 68, 762-769. PubMed id: 17510954 DOI: 10.1002/prot.21428

Date:

18-Dec-06 Release date: 26-Jun-07

Protein chains

O24313  (LEC1_PSOTE) -  Basic agglutinin from Psophocarpus tetragonolobus

Seq: 242 a.a.

Struc: 236 a.a.

DOI no: 10.1002/prot.21428

Proteins 68:762-769 (2007)

PubMed id: 17510954

Generation of blood group specificity: new insights from structural studies on the complexes of A- and B-reactive saccharides with basic winged bean agglutinin.

K.A.Kulkarni, S.Katiyar, A.Surolia, M.Vijayan, K.Suguna.

ABSTRACT

Basic winged bean agglutinin binds A-blood group substance with higher affinity and B-blood group substance with lesser affinity. It does not bind the O substance. The crystal structures of the lectin, complexed with A-reactive and B-reactive di and tri saccharides, have been determined. In addition, the complexes of the lectin with fucosylated A-trisaccharides and B-trisaccharides and with a variant of the A-trisaccharide have been modeled. These structures and models provide valuable insights into the structural basis of blood group specificities. All the four carbohydrate binding loops of the lectin contribute to the primary combining site while the loop of variable length contributes to the secondary binding site. In a significant advance to the current understanding, the interactions at the secondary binding site also contribute substantially, albeit in a subtle manner, to determine the blood group specificity. Compared with the interactions of the B-trisaccharide with the lectin, the third sugar residue of the A-reactive trisacharide forms an additional hydrogen bond with a lysine residue in the variable loop. In the former, the formation of such a hydrogen bond is prevented by a shift in the orientation of third sugar resulting from an internal hydrogen bond in it. The formation of this bond is also facilitated by an interaction dependent change in the rotamer conformation of the lysyl residue of the variable loop. Thus, the difference in the interactions at the secondary site is generated by coordinated movements in the ligand as well as the protein. A comparison of the crystal structure and the model of the complex involving the variant of the A-trisaccharide results in the delineation of the relative contributions of the interactions at the primary and the secondary sites in determining blood group specificity.

Selected figure(s)

Figure 1.
Figure 1. Dimeric structure of WBAI complexed with B-trisaccharide. Ca^2+ and Mn^2+ are shown as spheres. B-tri and N-linked glycans are shown in sticks.

Figure 2.
Figure 2. Electron density (2F[o]-F[c]) map of (a) A-tri (b) B-tri, (c) A-di and (d) B-di, contoured at 1 . Some sugar atoms are numbered.

The above figures are reprinted by permission from John Wiley & Sons, Inc.: Proteins (2007, 68, 762-769) copyright 2007.

Figures were selected by an automated process.