Purification and Characterization of a Novel Lectin with Antiphytovirus Activities from the wild Mushroom Paxillus involutus

A novel lectin was isolated from the dried fruiting bodies of the wild mushroom Paxillus involutus. Isolation was conducted by anion exchange chromatography on DEAE-Cellulose, Q-Sepharose and gel filtration on Superdex 75 using a fast protein liquid chromatography (FPLC) system. This lectin had a molecular mass of 28 kDa and was composed of four identical subunits, each with a molecular mass of 7 kDa. N-terminal amino acid sequence of the P. involutus lectin was determined to be CTCAVFLNNTTVKS, which showed a low level of similarity to mushroom lectin sequences reported previously. The biochemical properties of this lectin were determined, and the hemagglutinating activity was inhibited by inulin and O-Nitrophenyl-β-D-galacto-pyranoside. Additionally, Ca2+, Zn2+, Cd2+, Fe2+, and Al3+ inhibited its hemagglutinating activity, while Cu2+ promoted this activity. This lectin exhibited poor thermostability and was sensitive to HCl, but it had a high tolerance to NaOH exposure. In terms of biological properties, this lectin manifested antiphytovirus activity towards tobacco mosaic virus (TMV) with a 70.61% inhibition at a concentration of 200 µg/mL. This lectin was devoid of inhibitory activities toward pathogenic fungi and HIV-1 reverse transcriptase, and antiproliferative activities were observed in tumor cell lines including lung cancer A-549 and human colon cancer HCT-8 cells.