1lu2
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(New page: 200px<br /><applet load="1lu2" size="450" color="white" frame="true" align="right" spinBox="true" caption="1lu2, resolution 2.80Å" /> '''DOLICHOS BIFLORUS SE...)
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Revision as of 18:46, 20 November 2007
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DOLICHOS BIFLORUS SEED LECTIN IN COMPLEX WITH THE BLOOD GROUP A TRISACCHARIDE
Overview
The seed lectin (DBL) from the leguminous plant Dolichos biflorus has a, unique specificity among the members of the legume lectin family because, of its high preference for GalNAc over Gal. In addition, precipitation of, blood group A+H substance by DBL is slightly better inhibited by a blood, group A trisaccharide (GalNAc(alpha1-3)[Fuc(alpha1-2)]Gal) containing, pentasaccharide, and about 40 times better by the Forssman disaccharide, (GalNAc(alpha1-3)GalNAc) than by GalNAc. We report the crystal structures, of the DBL-blood group A trisaccharide complex and the DBL-Forssman, disaccharide complex.A comparison with the binding sites of Gal-binding, legume lectins indicates that the low affinity of DBL for Gal is due to, the substitution of a conserved aromatic residue by an aliphatic residue, (Leu127). Binding studies with a Leu127Phe mutant corroborate these, conclusions. DBL has a higher affinity for GalNAc because the N-acetyl, group compensates for the loss of aromatic stacking in DBL by making a, hydrogen bond with the backbone amide group of Gly103 and a hydrophobic, contact with the side-chains of Trp132 and Tyr104.Some legume lectins, possess a hydrophobic binding site that binds adenine and adenine-derived, plant hormones, i.e. cytokinins. The exact function of this binding site, is unknown, but adenine/cytokinin-binding legume lectins might be involved, in storage of plant hormones or plant growth regulation. The structures of, DBL in complex with adenine and of the dimeric stem and leaf lectin (DB58), from the same plant provide the first structural data on these binding, sites. Both oligomers possess an unusual architecture, featuring an, alpha-helix sandwiched between two monomers. In both oligomers, this, alpha-helix is directly involved in the formation of the hydrophobic, binding site. DB58 adopts a novel quaternary structure, related to the, quaternary structure of the DBL heterotetramer, and brings the number of, know legume lectin dimer types to four.
About this Structure
1LU2 is a Single protein structure of sequence from Vigna unguiculata subsp. cylindrica with A2G, CA and MN as ligands. Full crystallographic information is available from OCA.
Reference
Carbohydrate binding, quaternary structure and a novel hydrophobic binding site in two legume lectin oligomers from Dolichos biflorus., Hamelryck TW, Loris R, Bouckaert J, Dao-Thi MH, Strecker G, Imberty A, Fernandez E, Wyns L, Etzler ME, J Mol Biol. 1999 Mar 5;286(4):1161-77. PMID:10047489
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