The monosaccharide binding site of lentil lectin: an X-ray and molecular modelling study |
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Authors: | Remy Loris Florence Casset Julie Bouckaert Jurgen Pletinckx Minh-Hoa Dao-Thi Freddy Poortmans Anne Imberty Serge Perez Lode Wyns |
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Institution: | (1) Laboratorium voor Ultrastructuur, Instituut voor Moleculaire Biologie, Vrije Universiteit Brussel, Paardenstraat 65, B-1640 Sint-Genesius-Rode, Belgium;(2) Ingenierie Moléculaire, INRA, BP 527, 44026 Nantes cedex 03, France;(3) Vlaamse Instelling voor Technologisch Onderzoek—VITO, Boeretang 200, B-2400 Mol, Belgium;(4) LSO-CNRS, Faculté des Sciences et Techniques, 2 rue de la Houssinière, 44072 Nantes cedex 03, France |
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Abstract: | The X-ray crystal structure of lentil lectin in complex with -d-glucopyranose has been determined by molecular replacement and refined to anR-value of 0.20 at 3.0 Å resolution. The glucose interacts with the protein in a manner similar to that found in the mannose complexes of concanavalin A, pea lectin and isolectin I fromLathyrus ochrus. The complex is stabilized by a network of hydrogen bonds involving the carbohydrate oxygens O6, O4, O3 and O5. In addition, the -d-glucopyranose residue makes van der Waals contacts with the protein, involving the phenyl ring of Phe123 . The overall structure of lentil lectin, at this resolution, does not differ significantly from the highly refined structures of the uncomplexed lectin.Molecular docking studies were performed with mannose and its 2-O and 3-O-m-nitro-benzyl derivatives to explain their high affinity binding. The interactions of the modelled mannose with lentil lectin agree well with those observed experimentally for the protein-carbohydrate complex. The highly flexible Me-2-O-(m-nitro-benzyl)- -d-mannopyranoside and Me-3-O-(m-nitro-benzyl)- -d-mannopyranoside become conformationally restricted upon binding to lentil lectin. For best orientations of the two substrates in the combining site, the loss of entropy is accompanied by the formation of a strong hydrogen bond between the nitro group and one amino acid, Gly97 and Asn125 , respectively, along with the establishment of van der Waals interactions between the benzyl group and the aromatic amino acids Tyr100 and Trp128 .RL and FC are joint first authors. |
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Keywords: | lectin lentil lectin carbohydrate specificity glucose binding mannose binding |
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