Purification and Biochemical Characterization of Novel Galectin from the Black Poplar Medicinal Mushroom Cyclocybe cylindracea (Agaricomycetes) Strain MEST42 from Algeria.

In the present study, a new galectin designated Cyclocybe cylindracea lectin (CCL) was extracted from the fruiting bodies of the wild black popular mushroom C. cylindracea grown in Algeria. The protein was isolated using sepharose 4B as affinity chromatography matrix, and galactose as elutant. The purified galectin was composed of two subunits of 17.873 kDa each, with a total molecular mass of 35.6 kDa. Its agglutinant activity was impeded by galactose and its derivatives, as well as melibiose. Lactose showed the highest affinity, with a minimal inhibitory concentration of 0.0781 mM. CCL was sensitive to extreme pH conditions, and its binding function decreased when incubated with 10 mM EDTA, and it could be restored by metallic cations such as Ca2+, Mg2+, and Zn2+. CCL agglutinated human red blood cells, without any discernible specificity. Circular dichroism spectra demonstrated that its secondary structure contained ß-sheet as dominant fold. In addition, bioinformatics investigation on their peptide fingerprint obtained after MALDI-TOF/TOF ionization using mascot software confirmed that CCL was not like any previous purified lectin from mushroom: instead, it possessed an amino acid composition with high similarity to that of the putative urea carboxylase of Emericella nidulans (strain FGSC A4/ATCC 38163/CBS 112.46/NRRL 194/M139) with 44% of similarity score.

Characterization of Cytotoxic Lactose Binding Lectin from Sulphur Polypore, Laetiporus sulphureus (Agaricomycetes), from Algeria.

Mushroom lectins have important biological and biomedical applications. Most lectins purified from these organisms exhibit high toxicity in animal cells and toward microbial agents. They are able to induce cell growth inhibition and metabolism by their ability to interact with glyconjugate components (glycoproteins receptors, glycolipids) present in their membrane. After lectins bind to these membrane receptors, they induce cellular signalization chains in which gene expression is regulated and cell death programming (apoptosis) is activated. In this work, a new multimeric lectin was characterized from the rare saprobic edible mushroom, Laetiporus sulphureus strain TMES43, grown in the Algerian forest. Lectin was isolated with ammonium sulfate precipitation followed by affinity chromatography on a Sepharose 4B column, with specific activity of 1204.7 units of hemagglutination activity/mg and 35.55% yield. The protein has a tetrameric structure with a molecular weight of 36 kDa for each subunit, with a total molecular weight of approximately 140 kDa. In addition, a Mascot peptide fingerprint study on a matrix-assisted laser desorption ionization-time of flight tandem fragment showed identity with autophagy-related protein 16 from Meyerozyma guilliermondii (strain ATCC 6260/CBS 566/DSM 6381/JCM 1539/NBRC 10279/NRRL Y-324; Expasy ID: ATG16_PICGU) and no sequence similarity to known mushroom lectins. L. sulphureus hemagglutination activity was reduced by 5 mM of lactose and 10 mM of EDTA incubation and was recovered by metallic cations such as CaCl2, MgCl2, and ZnCl2. L. sulphureus purified lectin had no human ABO group specificity and showed low temperature and alkaline pH stabilities. The MTT preliminary assay showed that L. sulphureus purified lectin induced high cytotoxicity for tumor cells and normal cells.