STIMULATION OF HEMOLYTIC-ACTIVITY OF SEA-ANEMONE CYTOLYSINS BY 8-ANILINO-1-NAPHTHALENESULPHONATE

This study reports for the first time stimulation of protein activity by the hydrophobic probe, 8-anilino-1-naphthalenesulphonate (ANS). Mag nificalysin (HMg) I and II and equinatoxin (EqTx) II and III are cytol ysins isolated from the sea anemone Heteractis magnifica and Actinia e quina, respectively. The haemolytic activity of these cytolysins could be stimulated by treatment with ANS. Their activation involved confor mational changes following ANS treatment as shown by fluorescence spec tra. ANS-induced conformational changes were reversible upon removal o f ANS. ANS-stimulated activity of HMg I was inhibited by sphingomyelin and antiserum but not affected by bromosuccinimide (NBS) which oxidis es tryptophan residues. However, toxin pre-treated with NBS could no l onger be stimulated by addition of ANS. Energy transfer from tryptopha n to ANS was observed by a fluorescence scan. Hence the tryptophan res idues appear to be involved, at least partially, in ANS-binding, ANS-i nduced conformational change may be responsible for the activation of the cytolytic activity of these cytolysins. (C) 1997 Academic Press.