Screening for lectins from basidiomycetes and isolation of Punctularia atropurpurascens lectin

Aqueous extracts of basidiomycete fungi were screened for the presence of lectins by hemagglutination (HA) assays with mouse, rabbit, and sheep red blood cells. From mycelia and/or fruiting bodies, 23 extracts were prepared; 15 extracts exhibited HA activity towards mouse erythrocytes, with specific activities ranging from 12 to 440 lectin units (LU) mg(-1) protein. In HA inhibition assays, 43 carbohydrates including mono-, di-, tri-, tetrasaccharides, glycoproteins, and polysaccharides were tested as haptens, to determine the saccharide-binding specificities of the lectins. A novel lectin with specificity towards N-acetyl-glucosamine was purified from mycelia of Punctularia atropurpurascens using affinity chromatography on chitosan-Sepharose. The lectin has a subunit molecular mass of 67 kDa determined by SDS-PAGE and a pI of 5.0.