A lectin with mitogenic activity from the edible wild mushroom Boletus edulis

A melibiose- and xylose-cospecific homodimeric lectin was isolated from fresh fruiting bodies of Boletus edulis. The lectin was isolated using a protocol that consisted of ion exchange chromatography on DEAE-cellulose, affinity chromatography on CM-cellulose and gel filtration by fast protein liquid chromatography on Superdex 75. It was a dimer made up of two 16.3 kDa subunits. The hemagglutinating activity of the lectin was stable up to 40 °C, and in the presence of NaOH or HCl solutions up to a concentration of 25 mM. The hemagglutinating activity of the lectin was unaffected in the presence of AlCl3 and FeCl3 at and above 2 mM. MgCl2, ZnCl2 and MnCl2 inhibited the lectin activity. The lectin stimulated the mitogenic response of mouse splenocytes attaining a maximum at 1 μM, and inhibited human immunodeficiency virus-1 reverse transcriptase with an IC50 of 14.3 μM. It did not exhibit antifungal activity.