First Simultaneous Isolation of a Ribosome Inactivating Protein and an Antifungal Protein from a Mushroom (Lyophyllum shimeji) Together with Evidence for Synergism of their Antifungal Effects

From the fruiting bodies of the mushroom Lyophyllum shimeji, a novel ribosome inactivating protein with a molecular weight of 20 kDa and exhibiting antifungal activity against Physalospora piricola (IC50 = 2.5 μM) and Coprinus comatus was isolated. The protein, designated lyophyllin, was purified by ion exchange chromatography on CM–cellulose, affinity chromatography on Affi-gel Blue Gel, and then ion exchange chromatography on Mono S. Lyophyllin possessed an N-terminal sequence with some similarity to those of plant ribosome-inactivating proteins. It inhibited translation in rabbit reticulocyte lysate with an IC50 of 1 nM, thymidine uptake by murine splenocytes with an IC50 of 1 μM and HIV-1 reverse transcriptase activity with an IC50 of 7.9 nM. Lyophyllin did not manifest ribonuclease or hemagglutinating activity. An antifungal protein, designated Lyophyllum antifungal protein (LAP), with a molecular weight of 14 kDa, and an N-terminal sequence somewhat analogous to those of angiosperm thaumatin-like proteins and thaumatins and an inactive variant of the ubiquitin-conjugating enzyme, was first isolated from Lyophyllum shimeji. LAP was adsorbed on CM–cellulose, Affi-gel blue gel, and Mono S. LAP exerted antifungal activity against P. piricola (IC50 = 70 nM) and Mycosphaerella arachidicola but not against Rhizoctonia solani, Colletotrichum gossypii, and Coprinus comatus. It exerted very low translation inhibitory activity in a rabbit reticulocyte lysate system (IC50 = 70 μM) and negligible ribonuclease activity toward yeast transfer RNA and hemagglutinating activity toward rabbit erythrocytes. It inhibited HIV-1 reverse transcriptase with an IC50 of about 5.2 nM. A synergism in antifungal activities of LAP and lyophyllin against P. piricola was demonstrable.