Setsuko Iwanaga

A Novel Protein Toxin from the Deadly Box Jellyfish (Sea Wasp, Habu-kurage) Chiropsalmus quadrigatus

The deadly box jellyfish (Sea Wasp, Habu-kurage in Japanese) Chiropsalmus quadrigatus Haeckel (Cubozoa) is distributed widely in the tropical Pacific region. In Japan, three fatal cases due to stings from this species have been reported officially. We successfully isolated C. quadrigatus toxin-A (CqTX-A, 44 kDa), a major proteinaceous toxin, for the first time, from the nematocysts of C. quadrigatus. CqTX-A showed lethal toxicity to crayfish when administered via intraperitoneal injection (LD50=80 μg/kg) and hemolytic activity toward 0.8% sheep red blood cells (ED50= 160 ng/ml). Furthermore, we sequenced the cDNA encoding CqTX-A. The deduced amino acid sequence of CqTX-A (462 amino acids) showed 25.2% and 21.6% sequence similarity to Carybdea rastoni toxins (CrTXs) and Carybdea alata toxin-A (CrTX-A), respectively, which are Cubozoan jellyfish toxins.

Novel proteinaceous toxins from the nematocyst venom of the Okinawan sea anemone Phyllodiscus semoni Kwietniewski

The Okinawan sea anemone Phyllodiscus semoni is known to cause cases of severe stinging. We isolated P. semoni toxins 60A and 60B (PsTX-60A and PsTX-60B; ca. 60 kDa) as the major toxins from the isolated nematocysts of this species for the first time. PsTX-60A and PsTX-60B showed lethal toxicity to the shrimp Palaemon paucidence when administered via intraperitoneal injection (LD(50) values: 800-900 and 800 microg/kg, respectively) and hemolytic activity toward a 0.8% suspension of sheep red blood cells (ED(50) values: 600 and 300 ng/ml, respectively). Furthermore, we sequenced the cDNA encoding PsTX-60A. The deduced amino acid sequence of PsTX-60A did not show any similarity to previously reported proteins. The N-terminal amino acid sequence of PsTX-60B showed homology with that of PsTX-60A. These toxins represent a novel class of cytolytic proteinaceous toxins.

A New Polypeptide Toxin from the Nematocyst Venom of an Okinawan Sea Anemone Phyllodiscus semoni (Japanese name “unbachi-isoginchaku”)

The venomous sea anemone Phyllodiscus semoni causes cases of severe stinging. We isolated Phyllodiscus semoni toxin 20A (PsTX-20A), a hemolytic and lethal polypeptide (20 kDa), from the nematocyst venom of this species for the first time. Furthermore, we sequenced the cDNA encoding PsTX-20A. The deduced amino acid sequence of PsTX-20A showed that this toxin was a new member of the actinoporin family, which consists of several cytolytic polypeptides originating from sea anemones. PsTX-20A showed lethal toxicity to the shrimp Palaemon paucidens when administered via intraperitoneal injection (LD50, 50 μg/kg) and hemolytic activity toward 0.8% sheep red blood cells (ED50, 80 ng/ml).