Stonustoxin Is a Novel Lethal Factor from Stonefish (Synanceja horrida) Venom

Abstract

Stonustoxin (SNTX) is a multifunctional lethal protein isolated from venom elaborated by the stonefish, Synanceja horrida. It comprises two subunits, termed ␣ and ␤, which have respective molecular masses of 71 and 79 kDa. SNTX elicits an array of biological responses both in vitro and in vivo, particularly a potent hypotension that appears to be mediated by the nitric oxide pathway. As a prelude to structure-function studies, we have isolated and sequenced cDNA clones encoding the ␣-and ␤-subunits of SNTX from a venom gland cDNA library. The deduced amino acid sequence of neither subunit shows significant homology with any known protein. Protein sequence alignment does, however, show the subunits to be 50% homologous to each other and implies that they may have arisen from a common ancestor. The subunits of this novel toxin lack typical N-terminal signal sequences commonly found in proteins that are secreted via the endoplasmic reticulumGolgi apparatus pathway, indicating the possibility of its being secreted by a non-classical pathway, which is not clearly understood. The SNTX subunits have been expressed in Escherichia coli as cleavable fusion proteins that cross-react with antibodies raised against the native toxin. To the best of our knowledge, this is the first complete sequence of a fish-derived protein toxin to be reported.Stonefish are regarded as the most dangerous venomous fish in the world (1). Envenomation mediated by their venom apparatus elicits an array of symptoms, including an instantaneous and sharp pain at the site of the puncture wound, edema, hypotension, respiratory distress, convulsions, and death within 6 h (2-4). As with venoms produced by other organisms, stonefish venom is a mixture of enzymes and non-enzymatic proteins. Enzymatic activities detected in stonefish venom include hyaluronidase, alkaline phosphomonoesterase, 5Ј-nucleotidase, arginine amidase, arginine esterase, and proteinase activities (5). The hyaluronidase component from the venom of the stonefish Synanceja horrida has been purified (6). A proteinaceous lethal factor with a molecular weight of around 150,000 was first partially purified from the venom of S. horrida by Austin et al. (7). Subsequent to this, Deakins and Saunders (8) obtained a partially purified (10-fold) lethal factor from the same species. No further studies on this lethal protein were reported for the next 2 decades.Recently, we purified a lethal toxin from the venom of S. horrida, indigenous to the shallow waters of the Indo-Pacific oceans and designated it stonustoxin (SNTX) 1 (9). This toxin has a molecular weight of 148,000 and comprises two subunits, termed ␣ (71 kDa) and ␤ (79 kDa). It was found to be devoid of phospholipase A 2 , proteinase, and hyaluronidase activities, and had an LD 50 (intravenous) of 17 ng/g (9). Lethal factors have also been isolated from the venoms of other species of stonefish that display comparable biological activities. These include a 158-kDa cytolysin with lethal properties purified from the venom of Synanceja trach...

Stonefish toxin defines an ancient branch of the perforin-like superfamily

“…These symptoms include endothelium-dependent vasorelaxation, hemolytic activity, edema, increases in vascular permeability, myotoxic effects on the neuromuscular junction, and severe pain (1,3). By revealing that SNTX and related proteins are poreforming proteins of the MACPF/CDC superfamily, our data provide the structural and molecular context for the unique physiological effects of stonefish envenomation.…”

“…The lethal factor in stonefish venom is an ∼150-kDa protein termed stonustoxin (SNTX), an unusual example of a vertebrate cytolytic protein complex (2). SNTX is a soluble heterodimeric assembly of two closely related proteins termed SNTX-α and -β that share sequence identity of ∼50% (3). With the exception of a C-terminal PRY SPla and the RYanodine Receptor (PRYSPRY) domain in each protein (4), SNTX shares no obvious sequence similarity to any structurally or functionally characterized molecule.…”

Recent Progress in Jellyfish Toxin Study

“…2). Previous studies suggested that the amphiphilic structures of some cytolytic protein toxins allow the formation of pores in cell membranes, [11][12][13] and thus the amphiphilic structures of the box jellyfish toxins may explain their potent hemolytic activity (Table 1).…”

Structure of the PRYSPRY‐domain: Implications for autoinflammatory diseases

“…1). The SPRY domain is present for example in butyrophilin-related transmembrane glycoproteins (BTN) [3] and in stonustoxin SNTX, a cytolytic secreted protein [4]. Another set of proteins containing a SPRY domain are SSB proteins (SPRY domain associated with a SOCS box) belonging to the family of suppressors of cytokine signaling (SOCS) [5].…”