Isolation, properties and partial amino acid sequence of a new actinoporin from the sea anemone Radianthus macrodactylus

Elena V. Klyshko, Marina P. Issaeva, Margarita M. Monastyrnaya, Anna P. Il'yna, Konstantin V. Guzev, Tatyana I. Vakorina, Pavel S. Dmitrenok, Tatyana A. Zykova, Emma P. Kozlovskaya

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32 Scopus citations


A new cytolytic toxin, actinoporin RTX-S II, was isolated from the sea anemone Radianthus macrodactylus with a high degree of purity by a combination of gel filtration, ion-exchange and reverse-phase chromatography. RTX-S II has molecular mass of 19,280Da and isoelectric point of 10.0. The hemolytic activity of RTX-S II is inhibited by sphingomyelin. RTX-S II had an LD50 of 70 mg/kg, and is lacking in phospholipase activity. The amino acid composition of this protein contains a high amount of basic and non-polar amino acids and no cysteine. The N-terminal sequence of RTX-S II was determined. The partial amino acid sequence (141 aa) of RTX-S II was deduced based on the cDNA sequence obtained with two oligonucleotides encoding the N-terminal portion of RTX-S II and the internal conserved cytolysin peptide by PCR. A comparison of the RTX-S II cDNA sequence and the rtx-s II gene obtained with the same PCR primers indicates that they are 100% identical at the nucleotide level. It shows that no introns are present in the corresponding region of the rtx-s II gene. Multiple alignments of RTX-S II with known sequences of actinoporins show that RTX-S II is highly homologous to magnificalysin II from Heteractis magnifica. The predicted secondary structure of RTX-S II is predominantly anti-parallel β-structure, which is in good agreement with experimental data obtained from other sea anemones-actinoporins.

Original languageEnglish (US)
Pages (from-to)315-324
Number of pages10
Issue number3
StatePublished - Sep 1 2004

Bibliographical note

Funding Information:
The authors thank Dr I. Nazimov (Institute of Bioorganic Chemistry, the Russian Academy of Sciences, Moscow) for automated N-terminal amino acid sequence analyses of RTX-S II, and Mr A. Shvedov who translated this paper into English. This work was supported by the RFBR grant no. 02-04-49486, the program of Presidium of RAS “Molecular and cell biology” grant no. 03-1-0-05-002 and FEBRAS grant.


  • Actinoporins
  • Cytolysins
  • Hemolytic activity
  • Primary and secondary structures
  • Sea anemones
  • Sphingomyelin


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