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Received May 13, 2011; Revision received June 7, 2011
A new actinoporin Hct-S4 (molecular mass 19,414 ± 10 Da) belonging to the sphingomyelin-inhibited α-pore forming toxin (α-PFT) family was isolated from the tropical sea anemone Heteractis crispa (also called Radianthus macrodactylus) and purified by methods of protein chemistry. The N-terminal nucleotide sequence (encoding 20 amino acid residues) of actinoporin Hct-S4 was determined. Genes encoding 18 new isoforms of H. crispa actinoporins were cloned and sequenced. These genes form a multigene Hct-S family characterized by presence of N-terminal serine in the mature proteins. Highly conserved residues comprising the aromatic phosphorylcholine-binding site and significant structure–function changes in the N-terminal segment (10-27 amino acid residues) of actinoporins were established. Two expressed recombinant actinoporins (rHct-S5 and rHct-S6) were one order less hemolytically active than native actinoporins.
KEY WORDS: sea anemone, actinoporin, multigene Hct-S family, recombinant actinoporin, hemolytic activity, structure–function analysis