Characterization of a Novel Proteinous Toxin from Sea Anemone Actineria villosa

The sea anemone Actineria villosa expresses a lethal protein toxin. We isolated a novel 120-kDa protein, Avt120, from partially purified toxin and found it to possess extremely strong lethal activity. The 3,453-bp Avt120 gene translates to a 995-amino acid protein. The 50% lethal dose (LD 50 ) of purified Avt120 in mice was 85.17 ng. Among several tested cell lines, Colo205 cells were most sensitive to Avt120: 50% of them were damaged by 38.4 ng/mL Avt120. Avt120 exerted ATP degradation activity (10 μmol ATP h −1 mg −1 ), which was strongly inhibited by ganglioside GM1 to decrease the cytotoxicity of Avt120.