ROLE OF FREE THIOL-GROUPS IN THE BIOLOGICAL-ACTIVITIES OF STONUSTOXIN, A LETHAL FACTOR FROM STONEFISH (SYNANCEJA-HORRIDA) VENOM

Hoon Eng Khoo? Desong Chen and Raymond Yuen. Role of free thiol groups in the biological activities of stonustoxin, a lethal factor from sto nefish (Synanceja horrida) venom. Toxicon 36, 469-476, 1998.-Stonustox in (SNTX) is a two-subunit protein purified from the venom of a stonef ish, Synanceja horrida. It has potent lethal activity and is also a me mbrane poreforming cytolysin. The role of thiol groups in the biologic al activities of SNTX was investigated. Both the hemolytic and lethal activities of SNTX were potentiated by the reducing agent, dithiothrei tol (DTT). The hemolytic activity of SNTX was sensitive to the modific ation of thiol groups by 5,5'-dithiobis(3-nitrobenzoic acid) (DTNB). T he loss of haemolytic activity correlated with the number of thiol gro ups that were titrated with DTNB. Thiol modification of SNTX with DINE also inhibited its lethality. These inhibitory effects of thiol modif ication could be reversed by reduction with DTT. It was also found tha t the haemolytic activity of SNTX could not be inhibited by cholestero l. These observations indicate that free thiol groups play an importan t role in the haemolytic activity and lethality of SNTX but unlike oth er thiol-activated cytolysins, SNTX was not inhibited by cholesterol. Thus, SNTX may represent a new class of cytolytic toxin. (C) 1998 Else vier Science Ltd. Ail rights reserved.