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1.  Purification, partial characterization and preliminary X-ray diffraction analysis of a mannose-specific lectin from Cymbosema roseum seeds 
A lectin from C. roseum seeds (CRL) has been purified, characterized and crystallized.
A lectin from Cymbosema roseum seeds (CRL) was purified, characterized and crystallized. The best crystals grew in a month and were obtained by the vapour-diffusion method using a precipitant solution consisting of 0.1 M Tris–HCl pH 7.8, 8%(w/v) PEG 3350 and 0.2 M proline at a constant temperature of 293 K. A data set was collected to 1.77 Å resolution at a synchrotron-radiation source. CRL crystals are orthorhombic, belonging to space group P212121. Crystallographic refinement and full amino-acid sequence determination are in progress.
PMCID: PMC2197170  PMID: 16511310
Cymbosema roseum; Diocleinae; lectins
2.  Structure of a lectin from Canavalia gladiata seeds: new structural insights for old molecules 
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 Canavalia gladiata 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.
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.
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.
PMCID: PMC1955443  PMID: 17683532
3.  Effects of chloride channel blockers on hypotonicity-induced contractions of the rat trachea 
British Journal of Pharmacology  2003;141(2):367-373.
We have investigated the inhibitory effects of blockers of volume-activated (Clvol) and calcium-activated (ClCa) chloride channels on hypotonic solution (HS)-induced contractions of rat trachea, comparing their effects with those of the voltage-dependent calcium channel (VDCC) blocker nifedpine.HS elicited large, stable contractions that were partially dependent on the cellular chloride gradient; a reduction to 41.45±7.71% of the control response was obtained when extracellular chloride was removed. In addition, HS-induced responses were reduced to 26.8±5.6% of the control by 1 μM nifedipine, and abolished under calcium-free conditions, indicating a substantial requirement for extracellular calcium entry, principally via VDCCs.The established Clvol blockers tamoxifen (⩽10 μM) and 4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid (1–100 μM), at concentrations previously reported to inhibit Clvol in smooth muscle, did not significantly inhibit HS-induced contractions.In contrast, the recognized ClCa blocker niflumic acid (NFA; 1–100 μM) produced a reversible, concentration-dependent inhibition of HS responses, with a reduction to 36.6±6.4% of control contractions at the highest concentration. The mixed Clvol and ClCa blocker, 5-nitro 2-(3-phenylpropylamine) benzoic acid (NPPB; 10–100 μM) also elicited concentration-related inhibition of HS-induced contractions, producing a decrease to 35.9±11.3% of the control at 100 μM.Our results show that HS induces reversible, chloride-dependent contractions of rat isolated trachea that were inhibited by NFA and NPPB, while exhibiting little sensitivity to recognized blockers of Clvol. The data support the possibility that opening of calcium-activated chloride channels under hypotonic conditions in respiratory smooth muscle may ultimately lead to VDCC-mediated calcium entry and contraction.
PMCID: PMC1574202  PMID: 14691057
Volume sensitive; calcium-activated; chloride channels; trachea; niflumic acid; smooth muscle; contraction; hypotonicity

Results 1-3 (3)