BEL  -trefoil: A novel lectin with antineoplastic properties in king bolete (Boletus edulis) mushrooms

Abstract

A novel lectin was purified from the fruiting bodies of king bolete mushrooms (Boletus edulis, also called porcino, cep or penny bun). The lectin was structurally characterized i.e its amino acid sequence and three-dimensional structure were determined. The new protein is a homodimer and each protomer folds as β-trefoil domain and therefore we propose the name Boletus edulis lectin (BEL) β-trefoil to distinguish it from the other lectin that has been described in these mushrooms. The lectin has potent anti-proliferative effects on human cancer cells, which confers to it an interesting therapeutic potential as an antineoplastic agent. Several crystal forms of the apoprotein and of complexes with different carbohydrates were studied by X-ray diffraction. The structure of the apoprotein was solved at 1.12 Å resolution. The interaction of the lectin with lactose, galactose, N-acetylgalactosamine and T-antigen disaccharide, Galβ1-3GalNAc, was examined in detail. All the three potential binding sites present in the β-trefoil fold are occupied in at least one crystal form and are described in detail in this paper. No important conformational changes are observed in the lectin when comparing its co-crystals with carbohydrates with those of the ligand-free protein.

Entomotoxic and nematotoxic lectins and protease inhibitors from fungal fruiting bodies

“…In addition to these canonical sites, the β-trefoil fold can also harbor noncanonical carbohydrate-binding sites (Schubert et al 2012) and, as in case of protease inhibitors, binding sites for proteases (Žurga et al 2015) (see below). The best characterized representatives of this family of mushroom lectins are Rhizoctonia solani agglutinin (RSA) and Sclerotinia sclerotiorum agglutinin (SSA) of the plant pathogens R. solani (basidiomycete) (Hamshou et al 2013) and S. sclerotiorum (ascomycete) (Sulzenbacher et al 2010), as well as CNL, CCL2, MpL, and BEL β-trefoil of the homobasidio(agarico)mycetes Clitocybe nebularis (Pohleven et al 2009;Pohleven et al 2012), C. cinerea (Schubert et al 2012), Macrolepiota procera (Žurga et al 2014), and Boletus edulis (Bovi et al 2013) (Table 1). These proteins show high sequence variability, as they share only 7 to 16 % sequence identity (25 to 35 % similarity), the exception being CNL, MpL, and RSA that are 23 to 26 % identical (30 to 40 % similar).…”

“…While galectins bind linear glycans in a groove parallel to the protein surface, β-trefoil-type lectins bind them in a perpendicular orientation, in which only the non-reducing end of the glycan interacts with the binding pocket. All these proteins assemble to homodimers but, interestingly, each protein uses a different interface for dimer formation (Bovi et al 2013;Pohleven et al 2012;Schubert et al 2012;Skamnaki et al 2013;Sulzenbacher et al 2010;Žurga et al 2014).…”

A Novel Hemagglutinin with Antiproliferative Activity against Tumor Cells from the Hallucinogenic MushroomBoletus speciosus

“…However, some of them are toxic. There are only several reports about bioactive substance such as lectins [6, 7], ribonucleases [8], and toxic proteins [9] from this genus. Boletus speciosus is a rare wild hallucinogenic mushroom and can cause “lilliputian hallucination” when cooked in a wrong way or eaten too much.…”

Connaissances médicales utiles autour de la consommation du champignon Boletus edulis en 2014 : une revue de la littérature

“…La mesure de ces composés par différents outils physicochimiques -comme l'analyse spectrophotométrique de la réactivité au radical libre DPPH -révèle des capacités antioxydantes élevées pour B. edulis, en comparaison à diverses familles de champignons [16][17][18]. Par ailleurs, d'autres de ses composés -comme les lectines, glycoprotéines impliquées dans de nombreux processus de fonctionnement cellulaire -sont l'objet de travaux récents afin d'explorer de potentielles propriétés anticancéreuses ou antivirales associées à sa consommation [19,20].…”