1sbe

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spinqualitylabelsall models 1sbe, resolution 2.80Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

SOYBEAN AGGLUTININ FROM GLYCINE MAX

Overview

Soybean agglutinin (SBA) (Glycine max) is a tetrameric GalNAc/Gal-specific, lectin which forms unique cross-linked complexes with a series of, naturally occurring and synthetic multiantennary carbohydrates with, terminal GalNAc or Gal residues [Gupta et al. (1994) Biochemistry 33, 7495-7504]. We recently reported the X-ray crystal structure of SBA, cross-linked with a biantennary analog of the blood group I carbohydrate, antigen [Dessen et al. (1995) Biochemistry 34, 4933-4942]. In order to, determine the molecular basis of different carbohydrate-lectin, cross-linked lattices, a comparison has been made of the X-ray, crystallographic structures of SBA cross-linked with four isomeric analogs, of the biantennary blood group I carbohydrate antigen. The four, pentasaccharides possess the common structure of (beta-LacNAc)2Gal-beta-R, where R is -O(CH2)5COOCH3. The beta-LacNAc moieties in the four, carbohydrates are linked to the 2,3-, 2,4-, 3,6-, and 2,6-positions of the, core Gal residue(s), respectively. The structures of all four complexes, have been refined to approximately 2.4-2.8 A. Noncovalent lattice, formation in all four complexes is promoted uniquely by the bridging, action of the two arms of each bivalent carbohydrate. Association between, SBA tetramers involves binding of the terminal Gal residues of the, pentasaccharides at identical sites in each monomer, with the sugar(s), cross-linking to a symmetry-related neighbor molecule. While the 2,4-, 3,6-, and 2,6-pentasaccharide complexes possess a common P6422 space, group, their unit cell dimensions differ. The 2, 3-pentasaccharide, cross-linked complex, on the other hand, possesses the space group I4122., Thus, all four complexes are crystallographically distinct. The four, cross-linking carbohydrates are in similar conformations, possessing a, pseudo-2-fold axis of symmetry which lies on a crystallographic 2-fold, axis of symmetry in each lattice. In the case of the 3,6- and, 2,6-pentasaccharides, the symmetry of their cross-linked lattices requires, different rotamer orientations about their beta(1,6) glycosidic bonds. The, results demonstrate that crystal packing interactions are the molecular, basis for the formation of distinct cross-linked lattices between SBA and, four isomeric pentasaccharides. The present findings are discussed in, terms of lectins forming unique cross-linked complexes with glycoconjugate, receptors in biological systems.

About this Structure

1SBE is a Single protein structure of sequence from Glycine max with NAG, MN and CA as ligands. Full crystallographic information is available from OCA.

Reference

X-ray crystallographic studies of unique cross-linked lattices between four isomeric biantennary oligosaccharides and soybean agglutinin., Olsen LR, Dessen A, Gupta D, Sabesan S, Sacchettini JC, Brewer CF, Biochemistry. 1997 Dec 9;36(49):15073-80. PMID:9398234

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