A ubiquitin-like peptide from the mushroom Pleurotus sajor-caju exhibits relatively potent translation-inhibitory and ribonuclease activities

The fruiting bodies of the edible mushroom Pleurotus sajor-caju were extracted with an aqueous buffer and then subjected to affinity chromatography on Affi-gel Blue gel, ion exchange chromatography on DEAE-cellulose and gel filtration on Superdex 75. From the fraction of the extract adsorbed on Affi-gel Blue gel and unadsorbed on DEAE-cellulose, a 9.5 kDa peptide with an N-terminal sequence similar to ubiquitin was isolated with a yield of 0.25 mg/kg mushroom. The peptide inhibited cell-free translation with an IC(50) of 30 nM. It exhibited a ribonuclease activity of 450 U/mg toward yeast transfer RNA. The activities were substantially more potent than those of previously isolated mushroom ubiquitin-like protein and peptide.