A ribonuclease from sclerotia of the edible mushroom Pleurotus tuber-regium

A ribonuclease with a molecular weight of 29 kDa as determined by FPLC-gel filtration on Superose 12 was isolated from the sclerotia of the mushroom Pleurotus tuber-regium using a procedure involving extraction with aqueous buffer, ion exchange chromatography on DEAE-cellulose, affinity chromatography on Affigel blue gel, ion exchange chromatography on CM-cellulose, and FPLC on Mono S, The protein was unadsorbed on DEAE-cellulose but adsorbed on Affigel blue gel and CM-cellulose, It was homodimeric, made up of two identical subunits, each with a molecular weight of 14.5 kDa as witnessed in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It exhibited potent ribonucleolytic activity toward Poly G. Its ribonucleolytic activity was resistant to heating at 100 degrees C for 30 min, but was inhibited by HgCl2, ZnSO4, NiSO4, CaCl2, and Pb(NO3)(2). (C) 1998 Academic Press.