A cDNA encoding the 214-amino-acid (aa) precursor of equinatoxin V (EqtV) has been isolated from an Actinia equina cDNA library. The sequence of the mature toxin is preceded, as that of EqtII, by a signal peptide of 19 aa and a hydrophilic propeptide of 16 aa ending with a pair of basic residues. This is similar to the precursors of calitoxins from another sea anemone Calliactis parasitica and to those of some antimicrobial peptides of the magainin and dermaseptin families from vertebrates. The deduced aa sequence of the potential cell attachment Arg-Gly-Asp motif-containing EqtV shows 82% identity to that of EqtII.