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 1.8Å 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.