Purification and partial characterization of a novel anti-tumor glycoprotein from cultured mycelia of Grifola frondosa

A novel glycoprotein GFG-3a with the molecular weight of 88.01kDa and potent anti-tumor activity was isolated from the cultured mycelia of Grifola frondosa GF9801. GFG-3a was heat-sensitive with the decreasing anti-proliferative activity after treated from 56°C to 100°C for 10-120min. GFG-3a was a glycoprotein with O-glycosylation and contained 6.20% carbohydrate composed of d-arabinose, d-fructose, d-mannose, and d-glucose with a molar ratio of 1.33:4.51:2.46:1.00. FT-IR and NMR spectra proved that GFG-3a contained protein and carbohydrate portions with 3-O-methyl-galactose residues, (1→4)-linked β-galactose residues, and β-linked glucose residues. Circular dichroism (CD) revealed that GFG-3a was a predominantly β-sheet glycoprotein with a relatively small α-helical content. Protein sequencing and 3D model of GFG-3a were finally predicted by using MALDI-TOF-MS, NCBI blast search and online SWISS-MODLE Workspace service. Our findings will be a reference for the further structure-activity relationship analysis of the mushroom glycoproteins.