Abstract
The venom proteome of Hydrophis curtus (synonym: Lapemis hardwickii) from Penang, Malaysia was investigated with nano-electrospray ionization-liquid chromatography tandem mass spectrometry (ESI-LCMS/MS) of the reverse-phase high-performance liquid chromatography (HPLC) venom fractions. Thirty distinct protein forms were identified as toxins from ten families. The three major protein families were phospholipase A2 (PLA2, 62.0% of total venom proteins), three-finger toxin (3FTX, 26.33%) and cysteine-rich secretory protein (CRiSP, 9.00%). PLA2 comprises diverse homologues (11 forms), predominantly the acidic subtypes (48.26%). 3FTX composed of one short alpha-neurotoxin (SNTX, 22.89%) and four long alpha-neurotoxins (LNTX, 3.44%). Both SNTX and LNTX were lethal in mice (intravenous LD50 = 0.10 and 0.24 μg/g, respectively) but the PLA2 were non-lethal (LD50 >1 μg/g). The more abundant and toxic SNTX appeared to be the main driver of venom lethality (holovenom LD50 = 0.20 μg/g). The heterologous Sea Snake Antivenom (SSAV, Australia) effectively cross-neutralized the venom (normalized potency = 9.35 mg venom neutralized per g antivenom) and the two neurotoxins in vivo, with the LNTX being neutralized more effectively (normalized potency = 3.5 mg toxin/g antivenom) than SNTX (normalized potency = 1.57 mg/g). SSAV immunorecognition was strong toward PLA2 but moderate-to-weak toward the alpha-neurotoxins, indicating that neutralization of the alpha-neurotoxins should be further improved.
Highlights
The Elapidae family of venomous snakes consists of approximately 369 species in >60 genera
The venom chromatograms of H. curtus and its monophyletic cousin H. schistosus [12] both showed well resolved, less complex protein peaks in the following regions [27]: 30–35 min, 60–75 min and 90–120 min, which corresponded to the elution of Short alpha-neurotoxin (SNTX), Long alpha-neurotoxin (LNTX) and PLA2, respectively
The similar pattern of protein elution was reported for virtually all sea elapid venom profiles, and the three toxin groups typically constitute the bulk of the venom proteins at >95%, the individual protein subtypes and their individual expression could vary substantially at the inter- and intra-specific levels
Summary
The Elapidae family of venomous snakes consists of approximately 369 species in >60 genera (www.reptile-database.org). Toxins 2019, 11, 3 recent divergence of Australo-Melanesian elapids, resulting in two distinct subfamilies: (1) Elapinae, consisting of the paleogeographically-related Asian, African and American elapids; (2) Hydrophiinae, comprising the Australo-Melanesian elapids [1,2]. The aquatic elapids, generally referred to as sea snakes, form a large group of marine reptiles. It comprises the basal, semi-aquatic sea kraits (Laticauda sp., 6 species) and the more derived, densely complex true sea snakes (>50 species). The genus Hydrophis constitutes the core group of the true sea snakes. It is considered as a monophyletic clade by consensus today [3]
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