Novel peptide toxins from acrorhagi, aggressive organs of the sea anemone Actinia equina

Two peptide toxins, acrorhagin I (50 residues) and II (44 residues), were isolated from special aggressive organs (acrorhagi) of the sea anemone Actinia equina by gel filtration on Sephadex G-50 and reverse-phase HPLC on TSKgel ODS-120T. The LD50 against crabs of acrorhagin I and II were estimated to be 520 and 80 mu g/kg, respectively. 3'- and 5'-RACE established the amino acid sequences of the acrorhagin precursors. The precursor of acrorhagin I is composed of both signal and mature peptides and that of acrorhagin II has an additional sequence (propart) between signal and mature peptides. Acrorhagin I has no sequence homologies with any toxins, while acrorhagin II is somewhat similar to spider neurotoxins (hainantoxin-I from Selenocosmia hainana and Tx 3-2 from Phoneutria nigriventer) and cone snail neurotoxin (w-conotoxin MVIIB from Conus magus). In addition, analogous peptides (acrorhagin Ia and IIa) were also cloned during RT-PCR experiments performed to confirm the nucleotide sequences of acrorhagins. This is the first to demonstrate the existence of novel peptide toxins in the sea anemone acrorhagi. (c) 2005 Elsevier Ltd. All rights reserved.