Venomics Profiling of Thamnodynastes strigatus Unveils Matrix Metalloproteinases and Other Novel Proteins Recruited to the Toxin Arsenal of Rear-Fanged Snakes

Abstract

Rear-fanged and aglyphous snakes are usually considered not dangerous to humans because of their limited capacity of injecting venom. Therefore, only a few studies have been dedicated to characterizing the venom of the largest parcel of snake fauna. Here, we investigated the venom proteome of the rear-fanged snake Thamnodynastes strigatus , in combination with a transcriptomic evaluation of the venom gland. About 60% of all transcripts code for putative venom components. A striking finding is that the most abundant type of transcript (∼47%) and also the major protein type in the venom correspond to a new kind of matrix metalloproteinase (MMP) that is unrelated to the classical snake venom metalloproteinases found in all snake families. These enzymes were recently suggested as possible venom components, and we show here that they are proteolytically active and probably recruited to venom from a MMP-9 ancestor. Other unusual proteins were suggested to be venom components: a protein related to lactadherin and an EGF repeat-containing transcript. Despite these unusual molecules, seven toxin classes commonly found in typical venomous snakes are also present in the venom. These results support the evidence that the arsenals of these snakes are very diverse and harbor new types of biologically important molecules.

Colubrid Venom Composition: An -Omics Perspective

“…The Dipsadinae species studied include Philodryas olfersii [59], Thamnodynastes strigatus [60] and Hypsiglena sp. [12], as well as Erythrolamprus miliaris , Oxyrhopus guibei and Xenodon merremi described here.…”

“…Together with individual sequences isolated from other genera [9,50,56], 3FTx seem to be major components in many venoms of the subfamily Colubrinae. In contrast, in the Dipsadinae, 3FTx are not found [59,60] or are detected at minor abundance and diversity levels [57]. However, in the current work, we retrieved sequences from the transcriptome of the Duvernoy’s venom gland of Xenodon merremi (a dipsadine colubrid) that were expressed at high level (Table 1).…”

“…However, beta-defensin homologous genes were found in other viperid genera [86] and, more recently, venom gland transcripts were reported at relatively high expression levels in the transcriptome of the colubrids Thamnodynastes strigatus [60] and Phalotris mertensi [57]. In the latter, the corresponding protein was detected by shotgun MS/MS analysis of the venom, suggesting it may be a valid colubrid venom component.…”

“…In the latter, the corresponding protein was detected by shotgun MS/MS analysis of the venom, suggesting it may be a valid colubrid venom component. The colubrid proteins have a highly conserved signal peptide, almost identical to that of crotamine (see Supporting Figure 3 from [60]); the mature polypeptides display the same cysteines involved in the disulfide arrangement of crotamine, but the other residues are highly variable, making it difficult to establish the evolutionary relationship between them. …”

Natural Inhibitors of Snake Venom Metallopeptidases

“…DM43 has also been used as a bait protein in proteomic experiments aimed to exploit the metallopeptidase content of the rear-fanged snake Thamnodynastes strigatus (Ching et al 2011). In addition to binding canonical SVMPs, DM43 effectively interacted with svMMPs (snake venom matrix metallopeptidases).…”