BUL: a novel lectin from Bauhinia ungulataL. seeds with fungistatic and antiproliferative activities

A new galactose-binding lectin, termed BUL, has been purified from seeds of Bauhinia ungulata (Caesalpinoideae) by precipitation with solid ammonium sulfate followed by agarose-lactose affinity chromatography. B. ungulata lectin strongly agglutinated rabbit erythrocytes, both native and treated with proteolytic enzymes, and was inhibited by D-galactose and D-galactosederived sugars, especially N-acetyl-D-galactosamine. BUL was shown to be a stable glycoprotein, maintaining its hemagglutinating activity after incubation at wide ranges of temperature and pH, but not after incubation with EDTA. By SDS-PAGE analysis under reduced conditions, purified BUL showed an electrophoretic profile consisting of a single band with apparent molecular mass of 30 kDa. BUL showed intrinsic fluorescence typical of folded globular proteins, and circular dichroism spectra of lectin in the native state showed a predominance of b-sheet secondary structure. The N-terminal amino acid sequence of 19 residues showed a high sequential similarity to other galactose-specific lectins from the Bauhinia genus. In addition, BUL showed antifungal activity against phytopathogenic species and showed in vitro antiproliferative activity against the HT29 cell line of human colon adenocarcinoma in a dosedependent manner.