Purification and primary structure of a mannose/glucose-binding lectin fromParkia biglobosaJacq. seeds with antinociceptive and anti-inflammatory properties

Abstract

Parkia biglobosa (subfamily Mimosoideae), a typical tree from African savannas, possess a seed lectin that was purified by combination of ammonium sulfate precipitation and affinity chromatography on a Sephadex G-100 column. The P. biglobosa lectin (PBL) strongly agglutinated rabbit erythrocytes, an effect that was inhibited by d-mannose and d-glucose-derived sugars, especially α-methyl-d-mannopyranoside and N-acetyl-d-glucosamine. The hemagglutinating activity of PBL was maintained after incubation at a wide range of temperature and pH and also was independent of divalent cations. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, PBL exhibited an electrophoretic profile consisting of a single band with apparent molecular mass of 45 kDa. An analysis using electrospray ionization-mass spectrometry indicated that purified lectin possesses a molecular average mass of 47 562 ± 4 Da, and the analysis by gel filtration showed that PBL is a dimer in solution. The complete amino acid sequence of PBL, as determined using tandem mass spectrometry, consists of 443 amino acid residues. PBL is composed of a single non-glycosylated polypeptide chain of three tandemly arranged jacalin-related domains. Sequence heterogeneity was found in six positions, indicating that the PBL preparations contain highly homologous isolectins. PBL showed important antinociceptive activity associated to the inhibition of inflammatory process.