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The formula for calitoxin is C<sub>203</sub>H<sub>305</sub>N<sub>55</sub>O<sub>72</sub>S<sub>7</sub>. The ] is markedly dissimilar from other known sea anemones toxins. There are two known genes coding for two highly ] calitoxins. They are CLX-1 and CLX-2, both consisting of 46 amino acids. Both originate from a ] of 79 amino acids where the ] determines whether it will be the mature CLX-1 or CLX-2. In the mature CLX, one ] is responsible for a single ] to ] replacement in the coding region of CLX-2, leading to the difference between the two peptides. The structural organization of these two genes show a high degree of homology. This might imply that the two different peptides have the same biological function. This cannot yet be confirmed because only CLX-1 has been isolated from ''C. parasitica''.<ref name="spag" />
The formula for calitoxin is C<sub>203</sub>H<sub>305</sub>N<sub>55</sub>O<sub>72</sub>S<sub>7</sub>. The ] is markedly dissimilar from other known sea anemones toxins. There are two known genes coding for two highly ] calitoxins. They are CLX-1 and CLX-2, both consisting of 46 amino acids with three ]s.<ref name=Kastin> Both originate from a ] of 79 amino acids where the ] determines whether it will be the mature CLX-1 or CLX-2. In the mature CLX, one ] is responsible for a single ] to ] replacement in the coding region of CLX-2, leading to the difference between the two peptides. The structural organization of these two genes show a high degree of homology. This might imply that the two different peptides have the same biological function. This cannot yet be confirmed because only CLX-1 has been isolated from ''C. parasitica''.<ref name="spag" />
Calitoxin, also known as CLX, is a sea anemone toxin which increases neurotransmitter release at invertebrate neuromuscular junctions. Two different toxins, namely CLX-1 and CLX-2, can be distinguished. It targets crabs and octopuses, among other invertebrates.
Calitoxin is a highly potent neurotoxin. It is produced by the sea anemone Calliactis parasitica and stored in the nematocysts of stinging cells (cnidocytes). This sea anemone is a species from the Hormathiidae family and is present along the European coasts of the Atlantic Ocean and in the Mediterranean Sea.
Structure and chemistry
The formula for calitoxin is C203H305N55O72S7. The amino acid sequence is markedly dissimilar from other known sea anemones toxins. There are two known genes coding for two highly homologous calitoxins. They are CLX-1 and CLX-2, both consisting of 46 amino acids with three disulfide bonds.Cite error: A <ref> tag is missing the closing </ref> (see the help page). In a natural setting, C. parasitica establishes a mutualistic relationship with the hermit crab Pagurus bernhardus. The sea anemone identifies shells inhabited by the hermit crab and attaches. Through stings against potential predators, C. parasitica provides protection for the hermit crab. In return, the sea anemone gains an advantage in accessing a broader distribution of food sources, as the crab moves across the ocean floor. Octopuses will avoid shells bearing C. parasitica.
Toxicity
Calitoxin has been tested for activity on the crab Carcinus mediterraneus, by injecting a 0.1 mL solution with 0.2 µg lyophilized CLX of into the hemocoel. This revealed that the toxic unit corresponds to this minimum amount of the toxin inducing muscle contractions in the crab causing paralysis within 1 minute from injection. The LD50 is unknown.
References
^ Cariello, L; de Santis, A; Fiore, F; Piccoli, R; Spagnuolo, A; Zanetti, L; Parente, A (21 Mar 1989). "Calitoxin, a neurotoxic peptide from the sea anemone Calliactis parasitica: amino acid sequence and electrophysiological properties". Biochemistry. 28 (6): 2484–9. PMID2567180. {{cite journal}}: |access-date= requires |url= (help)
^ Spagnuolo, Antonietta; Zanetti, Laura; Cariello, Lucio; Piccoli, Renata. "Isolation and characterization of two genes encoding calitoxins, neurotoxic peptides from Calliactis parasitica (Cnidaria)". Gene. 138 (1–2): 187–191. doi:10.1016/0378-1119(94)90805-2.
