Purification and Characterization of Two Lectins from Callus of<i>Helianthus tuberosus</i>

Abstract

Two lectins were purified from Helianthus tuberosus callus by maltose affinity chromatography and subsequent preparative electrophoresis. The lectins were designated HTA I and HTA II and their molecular masses were about 34 kDa by gel-filtration chromatography. A single band of 17 kDa and bands of 17 kDa and 18 kDa were detected after SDS-PAGE of HTA I and HTA II, respectively, indicating that HTA I is a homodimer while HTA II is a heterodimer. The amino acid compositions of the two lectins were very similar; they were rich in glycine residues, lacking detectable amounts of methionine, cysteine, and histidine. A hapten-inhibition assay showed that HTA I and HTA II had identical saccharide-binding specificity to the extent tested and belonged to the group of so-called mannose/glucose-binding lectins. They had high affinity for alpha-linked manno-oligosaccharides. Each HTA completely lost its hemagglutinating activity at pH 5.0, as a result of its dissociation to monomers, but it did not lose its ability to bind to oligosaccharides.