Isolation of a new ribonuclease from fresh fruiting bodies of the straw mushroom

Although ribonucleases have been isolated from numerous organisms in the animal and plant kingdoms, only a few have been reported from mushrooms, In this investigation, a novel ribonuclease, with an N-terminal annino acid sequence distinctly different from those of the previously published mushroom ribonucleases, was isolated from the fruiting bodies of the straw mushroom. It exhibited a molecular weight of 42.5 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis which was larger than those of ribonucleases from other organisms. The isolation procedure entailed extraction with aqueous buffer, (NH4)(2)SO4 precipitation, ion exchange chromatography on DEAE-cellulose, affinity chromatography on Affi-gel blue gel, ion exchange chromatography on CM-Sepharose CL6B, and gel filtration on Superdex 75 using fast protein liquid chromatography. Straw mushroom ribonuclease was relatively specific for polyU and hydrolyzed yeast tRNA with a pH optimum between 6.5 and 7.5. (C) 1999 Academic Press.