Purification, cloning and characterization of fragaceatoxin C, a novel actinoporin from the sea anemone Actinia fragacea

Actinia fragacea is commonly called the “strawberry” anemone because of the distinctive yellow or green spots displayed on its red column. Its venom contains several haemolytic proteins with a molecular mass of ∼20 kDa that can be separated by ion-exchange column chromatography. One of them was purified to homogeneity and was named fragaceatoxin C (FraC). Its 15 N-terminal residues were identified by Edman degradation and served to obtain its complete DNA coding sequence by RT-PCR. The coding region of FraC was amplified and cloned in the expression vector pBAT-4. Purified recombinant FraC consists of 179 amino acids and multiple sequence alignment with other actinoporins clearly indicates that FraC belongs to this protein family. The secondary structure, thermal stability and lytic activity of native and recombinant FraC were practically identical and exhibit the same basic features already described for equinatoxin-II and sticholysin-II.