Ribotoxins are a more widespread group of proteins within the filamentous fungi than previously believed

alpha-Sarcin, restrictocin and mitogillin are the best known members of the family of fungal ribotoxins. In recent years, new members of this family h ave been discovered and characterised. In this work, we study the occurrenc e of ribotoxins among different species of fungi. The presence of ribotoxin s has been identified in some new species by means of genetic studies, as w ell as expression and activity assays. The ribotoxin genes have been partia lly sequenced, and demonstrate a high degree of similarity. These studies d emonstrate that these toxins are more widespread than previously considered . This is surprising, considering the ribotoxins are such specific and pote nt toxins, of unknown biological function. These studies confirm the hypoth esis that these proteins are naturally engineered toxins derived from ribon ucleases of broad substrate specificity. (C) 1999 Elsevier Science Ltd. All rights reserved.