Structure of a lectin from Canavalia gladiata seeds: new structural insights for old molecules

<p>Abstract</p> <p>Background</p> <p>Lectins are mainly described as simple carbohydrate-binding proteins. Previous studies have tried to identify other binding sites, which possible recognize plant hormones, secondary metabolites, and isolated amino acid residues. We report the crystal structure of a lectin isolated from <it>Canavalia gladiata </it>seeds (CGL), describing a new binding pocket, which may be related to pathogen resistance activity in ConA-like lectins; a site where a non-protein amino-acid, α-aminobutyric acid (Abu), is bound.</p> <p>Results</p> <p>The overall structure of native CGL and complexed with α-methyl-mannoside and Abu have been refined at 2.3 Å and 2.31 Å resolution, respectively. Analysis of the electron density maps of the CGL structure shows clearly the presence of Abu, which was confirmed by mass spectrometry.</p> <p>Conclusion</p> <p>The presence of Abu in a plant lectin structure strongly indicates the ability of lectins on carrying secondary metabolites. Comparison of the amino acids composing the site with other legume lectins revealed that this site is conserved, providing an evidence of the biological relevance of this site. This new action of lectins strengthens their role in defense mechanisms in plants.</p

Structural basis for both pro- and anti-inflammatory response induced by mannose-specific legume lectin from Cymbosema roseum

Legume lectins, despite high sequence homology, express diverse biological activities that vary in potency and efficacy. In studies reported here, the mannose-specific lectin from Cymbosema roseum (CRLI), which binds N-glycoproteins, shows both pro-inflammatory effects when administered by local injection and anti-inflammatory effects when by systemic injection. Protein sequencing was obtained by Tandem Mass Spectrometry and the crystal structure was solved by X-ray crystallography using a Synchrotron radiation source. Molecular replacement and refinement were performed using CCP4 and the carbohydrate binding properties were described by affinity assays and computational docking. Biological assays were performed in order to evaluate the lectin edematogenic activity. The crystal structure of CRLI was established to a 1.8 Å resolution in order to determine a structural basis for these differing activities. The structure of CRLI is closely homologous to those of other legume lectins at the monomer level and assembles into tetramers as do many of its homologues. The CRLI carbohydrate binding site was predicted by docking with a specific inhibitory trisaccharide. CRLI possesses a hydrophobic pocket for the binding of α-aminobutyric acid and that pocket is occupied in this structure as are the binding sites for calcium and manganese cations characteristic of legume lectins. CRLI route-dependent effects for acute inflammation are related to its carbohydrate binding domain (due to inhibition caused by the presence of α-methyl-mannoside), and are based on comparative analysis with ConA crystal structure. This may be due to carbohydrate binding site design, which differs at Tyr12 and Glu205 position. © 2011 Elsevier Masson SAS. All rights reserved

Structure of a lectin from seeds: new structural insights for old molecules-4

<p><b>Copyright information:</b></p><p>Taken from "Structure of a lectin from seeds: new structural insights for old molecules"</p><p>http://www.biomedcentral.com/1472-6807/7/52</p><p>BMC Structural Biology 2007;7():52-52.</p><p>Published online 2 Aug 2007</p><p>PMCID:PMC1955443.</p><p></p> +18 (m/z = 1419.8669) to + 28 (m/z = 913.1152). (B) Deconvolution of CGL spectrum, showing the double-charged ion (m/z = 12770.0010) and the mono-charged ion (m/z = 25541.0020) which represents the exact mass of the protein. (C) The Abu signature is represented by the peak with m/z (+H) = 104.1131 ± 0.1 M. The presence of Abu in the CGL structure was confirmed by MS/MS analysis. The spectrum reveals an Abu fragmentation ion displaying m/z = 86.05 ± 0.1, this mass referred to Abu molecular mass with a common loss of a water group (~18 Da)

Structure of a lectin from seeds: new structural insights for old molecules-5

<p><b>Copyright information:</b></p><p>Taken from "Structure of a lectin from seeds: new structural insights for old molecules"</p><p>http://www.biomedcentral.com/1472-6807/7/52</p><p>BMC Structural Biology 2007;7():52-52.</p><p>Published online 2 Aug 2007</p><p>PMCID:PMC1955443.</p><p></p>h concentration during the plant ontogeny. (●) represents the Abu concentration during the seeding as reported by Rozan .[12]; (■) refers to the lectin concentration determined by Da Silva .[22]; and (▲) gives the concentration of compounds related to pathogens response and stress events in accord to Boege K & Marquis R J[11]