ABSTRACT
Plant lectins, especially those purified from species of the Leguminosae family, represent the best-studied group of carbohydrate-binding proteins. Lectins purified from seeds of the Diocleinae subtribe exhibit a high degree of sequence identity notwithstanding that they show very distinct biological activities. Two main factors have been related to this feature: variance in key residues influencing the carbohydrate-binding site geometry and differences in the pH-dependent oligomeric state profile. In this work, we have isolated a lectin from Canavalia boliviana (Cbol) and solved its x-ray crystal structure in the unbound form and in complex with the carbohydrates Man(α1-3)Man(α1-O)Me, Man(α1-4)Man(α1-O)Me and 5-bromo-4-chloro-3-indolyl-α-D-mannose. We evaluated its oligomerization profile at different pH values using Small Angle X-ray Scattering and compared it to that of Concanavalin A. Based on predicted pKa-shifts of amino acids in the subunit interfaces we devised a model for the dimer-tetramer equilibrium phenomena of these proteins. Additionally, we demonstrated Cbol anti-inflammatory properties and further characterized them using in vivo and in vitro models.
Subject(s)
Anti-Inflammatory Agents/pharmacology , Canavalia/chemistry , Edema/drug therapy , Mannosides/chemistry , Peritonitis/drug therapy , Plant Lectins/chemistry , Plant Lectins/pharmacology , Seeds/chemistry , Amino Acid Sequence , Animals , Binding Sites , Cell Movement/drug effects , Chemotaxis/drug effects , Crystallography, X-Ray , Edema/chemically induced , Mannosides/metabolism , Models, Molecular , Molecular Sequence Data , Neutrophils/cytology , Neutrophils/drug effects , Peritonitis/chemically induced , Protein Conformation , Rats , Rats, Wistar , Sequence Homology, Amino Acid , Spectrometry, Mass, Electrospray IonizationABSTRACT
The aim of the present study was to evaluate the potential antinociceptive and toxicity of Canavalia boliviana lectin (CboL) using different methods in mice. The role of carbohydrate-binding sites was also investigated. CboL given to mice daily for 14 days at doses of 5 mg/kg did not cause any observable toxicity. CboL (1, 5, and 10 mg/kg) administered to mice intravenously inhibited abdominal constrictions induced by acetic acid and the two phases of the formalin test. In the hot plate and tail immersion tests, the same treatment of CboL induced significant increase in the latency period. In the hot plate test, the effect of CboL (5 mg/kg) was reversed by naloxone (1 mg/kg), indicating the involvement of the opioid system. In the open-field and rota-rod tests, the CboL treatment did not alter animals' motor function. These results show that CboL presents antinociceptive effects of both central and peripheral origin, involving the participation of the opioid system via lectin domain.
