Cobra Three-Finger Toxins Interact with RNA and DNA: Nucleic Acids as Their Putative Biological Targets.

Three-finger toxins (TFTs), including neurotoxins and cytotoxins, form one of the largest families of snake venom proteins and interact with various biological targets. Neurotoxins target proteinaceous receptors while cytotoxins interact mainly with the lipids of cell membranes and to a lesser extent with carbohydrates. However, no data about the interaction of TFTs with nucleic acids can be found. To detect this interaction, we applied spectrophotometry, ion-paired HPLC and electrophoretic mobility shift assay (EMSA). Using spectrophotometry, we found that TFTs from cobra venom increased the optical density of an RNA solution in a time-dependent manner indicating toxin interaction with RNA. A decrease in the net negative charge of the RNA molecule upon interaction with neurotoxin II from cobra venom was revealed by ion-pair HPLC. EMSA showed decreased electrophoretic mobility of both RNA and DNA upon addition of different TFTs including the non-conventional cobra toxin WTX and water-soluble recombinant human three-finger protein lynx1. We suggest that the interaction with nucleic acids may be a common property of TFTs, and some biological effects of TFTs, for example, cytotoxin-induced apoptosis in cancer cell lines, may be mediated by interaction with nucleic acids.