Stimulation of haemolytic activity of sea anemone cytolysins by 8-anilino-1-naphthalenesulphonate

Abstract

This study reports for the first time stimulation of protein activity by the hydrophobic probe, 8-anilino-1-naphthalenesulphonate (ANS). Magnificalysin (HMg) I and II and equinatoxin (EqTx) II and III are cytolysins isolated from the sea anemone Heteractis magnifica and Actinia equina, respectively. The haemolytic activity of these cytolysins could be stimulated by treatment with ANS. Their activation involved conformational changes following ANS treatment as shown by fluorescence spectra. ANS-induced conformational changes were reversible upon removal of ANS. ANS-stimulated activity of HMg I was inhibited by sphingomyelin and antiserum but not affected by bromosuccinimide (NBS) which oxidises tryptophan residues. However, toxin pre-treated with NBS could no longer be stimulated by addition of ANS. Energy transfer from tryptophan to ANS was observed by a fluorescence scan. Hence the tryptophan residues appear to be involved, at least partially, in ANS-binding. ANS-induced conformational change may be responsible for the activation of the cytolytic activity of these cytolysins.