Fungal Ribotoxin
Fungal ribotoxins are a group of extracellular ribonucleases (RNases) secreted by fungi. Their most notable characteristic is their extraordinary specificity. They inactivate ribosomes by cutting a single phosphodiester bond of the rRNA that is found in a universally conserved sequence. This cleavage leads to cell death by apoptosis. However, since they are extracellular proteins, they must first enter the cells that constitute their target to exert their cytotoxic action. This entry constitutes the rate-determining step of their action. No protein receptor has been found. Thus, in order to penetrate the cells, they must take advantage of changes in permeability and the biophysical properties of the membranes, produced by phenomena such as tumour transformation or a viral infection. This is why α-sarcin, the most representative member of the group, was originally discovered as an antitumoural agent. However, it turned out not to be as safe as needed and the research in this fi ...
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