NOVEL POLYPEPTIDE TOXINS WITH CRAB LETHALITY FROM THE SEA-ANEMONE ANEMONIA-ERYTHRAEA

The sea anemone Anernonia erythraea was found to contain polypeptide t oxins with crab lethality as well as hemolysins. Three polypeptide tox ins (AETX I, II and III) were isolated by gel filtration on Sephadex G -50 and reverse-phase HPLC on TSKgel ODS-120T. A geographic variation in toxin composition was suggested. The LD50 against crabs of AETX I, II and III were estimated to be 2.2, 0.53 and 0.28 mu g/kg, respective ly, but none of the toxins showed lethality in mice. The amino acid se quences of the three toxins were deduced from sequencings of the whole molecules and their enzymatic fragments. Amino acid analyses and mole cular mass determinations supported the accuracy of the deduced sequen ces. AETX I, comprising 47 amino acid residues including 6 half-Cys re sidues, is an analog of sea anemone type 1 toxins. On the other hand, AETX II and III, which are highly homologous with each other, are quit e distinct from the known sea anemone polypeptide toxins in that they are composed of 59 residues including 10 half-Cys residues. Interestin gly, both toxins have sequence similarities with neurotoxins isolated from the Brazilian 'armed' spider Phoneutria nigriventer.