THE ROLE OF CATIONIC AMINO-ACID-RESIDUES IN THE LETHAL ACTIVITY OF STONUSTOXIN FROM STONEFISH (SYNANCEJA-HORRIDA) VENOM

Stonustoxin (SNTX) is a two subunit pore-forming cytolytic protein pur ified from the venom of the stonefish (Synanceja horrida). SNTX also p ossesses lethal activity. Since cationic residues contribute significa ntly to the cytolytic activity of several pore-forming toxins, we exam ined the role of lysine and arginine residues in the lethal activity o f SNTX. SNTX lost its lethal activity when the positively-charged side chains of lysine residues were converted to negatively-charged side c hains upon succinylation. When the arginine residues were modified usi ng 2,3-butanedione, SNTX also lost its lethal activity. However, the d omains for cytolytic and lethal activity may not necessarily be the sa me.