Purification and characterization of a novel immunomodulatory protein from the medicinal mushroom Trametes versicolor

Bioactive proteins represent an important group of functional agents in medicinal mushrooms.Trametes versicolor(L.) Lloyd is a mushroom frequently used in traditional Chinese medicine for its anti-tumor and immunomodulatory activities.A new immunomodulatory protein from T.versicolor,named TVC,was purified by ammonium sulfate precipitation,ion-exchange chromatography and gel filtration chromatography.Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the purified protein revealed a single band with a molecular weight of 15.0 kD.Native polyacrylamide gel analysis revealed a band at 30 kD,indicating that TVC exists in solution as a homodimer.Isoelectric focusing showed that TVC was an acidic protein with an isoelectric point of 4.0.TVC was found to lack carbohydrate modifications(based on periodic acid/Schiff staining) and it does not agglutinate mouse red blood cells,suggesting that TVC is not a lectin-like protein.Biological activity assays dem-onstrated that TVC can enhance the proliferation of splenocytes,while it has no stimulatory effects on CD4+and CD8+T cells. TVC markedly increases the proliferation of human peripheral blood lymphocytes in a dose-dependent manner and enhances the production of both nitric oxide and tumor necrosis factor-alpha by lipopolysaccharide-induced murine macrophages.The results indicate that TVC is an immunostimulant that can boost immune response.Comparison of the N-terminal amino acid residues and mass spectrometry results with the protein database revealed no homologous proteins.