Purification and characterization of a novel lectin from the toxic wild mushroom Inocybe umbrinella

From the dried fruiting bodies of the toxic mushroom Inocybe umbrinella, a novel lectin with a molecular mass of 17 kDa has been isolated with about 160-fold purification. The purification protocol comprised ion exchange chromatography on DEAE-cellulose, and CM-cellulose, and gel filtration on Superdex 75. Among the carbohydrates tested, raffinose, D-melibiose, a-lactose and D(+)-galactose could inhibit the hemagglutinating activity of the lectin. The hemagglutinating activity was stable between 10 and 60 degrees C, in 12.5-100 mM HCl, and in 50 mM NaOH. The hemagglutinating activity was inhibited by Ca2+, Mn2+ and Mg2+ ions, but was unaffected by Fe3+, Zn2+ and Al3+ ions. The lectin inhibited HIV-1 reverse transcriptase with an IC50 of 4.7 +/- 0.2 mu M. Proliferation of tumor cells including hepatoma HepG2 cells and breast cancer MCF7 cells was inhibited by the lectin with an IC50 of 3.5 +/- 0.2 mu M and 7.4 +/- 0.3 mu M, respectively. The lectin has a unique N-terminal amino acid sequence, DGVLATNAVA. It did not exhibit antifungal activity. The present report is the first on an Inocybe lectin and represents one of the very few reports on lectins from toxic mushrooms. (C) 2008 Elsevier Ltd. All rights reserved.