Flammin and velin: new ribosome inactivating polypeptides from the mushroom Flammulina velutipes.

A protein designated flammin and exhibiting a molecular mass of 30kDa, and another protein designated velin and possessing a molecular mass of 19 kDa, were isolated from the fruiting bodies of the edible mushroom Flammulina velutipes. Flammin and velin inhibited translation in a rabbit reticulocyte lysate system with an IC(50) of 1.4 and 2.5 nM, respectively. Flammin demonstrated only a small degree of resemblance in N-terminal sequence to angiosperm type 1 ribosome inactivating proteins (RIPs) such as trichosanthin, alpha-momorcharin and beta-momorcharin but no sequence similarity to other mushroom RIPs. Velin manifested limited sequence homology to the A chain of abrin, a type 2 angiosperm RIP. Neither flammin nor velin showed any ribonuclease or protease activity. Both flammin and velin were unadsorbed on DEAE-cellulose and adsorbed on Affi-gel blue gel and CM-Sepharose. They were separable in gel filtration on Superdex 75 by fast protein liquid chromatography.