A Novel Ribonuclease with Potent HIV-1 Reverse Transcriptase Inhibitory Activity from Cultured Mushroom Schizophyllum commune

A 20-kDa ribonuclease (RNase) was purified from fresh fruiting bodies of cultured Schizophyllum commune mushrooms. The RNase was not adsorbed on Affi-gel blue gel but adsorbed on DEAE-cellulose and CM-cellulose. It exhibited maximal RNase activity at pH 6.0 and 70 degrees C. It demonstrated the highest ribonucleolytic activity toward poly (U) (379.5 mu/mg), the second highest activity toward poly (C) (244.7 mu/mg), less activity toward poly (A) (167.4 mu/mg), and much weaker activity toward poly (G) (114.5 mu/mg). The RNase inhibited HIV-1 reverse transcriptase with an IC50 of 65 mu M. No effect on [H-3-methyl]-thymidine uptake by lymphoma MBL2 cells and leukemia L1210 cells was observed at 100 mu M concentration of the RNase. A comparison of RNases from S. commune and Volvariella volvacea revealed that they demonstrated some similarities in N-terminal amino acid sequence, optimum pH and polyhomoribonucleotide specificity. However, some differences in chromatographic behavior and molecular mass were observed.