A rapid and effective method for purification of a heat-resistant lectin from potato (Solanum tuberosum) tubers.

The potato lectin has been identified to consist of two chitin-binding modules, each containing twin hevein domains. Based on the thermotolerance of the hevein polypeptide, a simple, rapid, and effective protocol for the small-scale purification of the potato lectin has been developed in this study. The method involves only one anion exchange chromatographic step beyond the ammonium sulfate precipitation and the heating treatment. With this method, the potato lectin, a glycoprotein with molecular mass of approximately 60 kDa was found and purified to homogeneity with 9513.3 u/mg of specific hemagglutination (HA) activity in 76.8% yield. The homogeneity was confirmed by SDS-PAGE electrophoresis and reverse-phase HPLC analysis. The purified lectin was identified using MS-based peptide sequencing (MALDI-TOF/TOF) and showed a 100% Confidence Interval as being homologous to hevein domains in potato lectin. The periodic acid-Schiff staining and ferric-orcinol assay for pentose, as well as its HA activity inhibition by chitosan oligomers further confirmed the purified lectin as a potato chitin-binding lectin. It is noteworthy that the purified potato lectin exhibited heat resistance, by which, together with a short time precipitation by ammonium sulfate, more than 96% of the total proteins in the crude extract were removed. The lectin therefore was easily resolved from the other remining proteins on a DEAE-methyl polyacrylate column.