Abstract
The spine-bellied sea snake (Hydrophis curtus) is known to cause human deaths, yet its venom composition has not yet been proteomically characterised. An in-depth proteomic analysis was performed on H. curtus venom from two different seasons, January and June, corresponding to adults and subadults, respectively. Venoms from adult and subadult H. curtus individuals were compared using reversed-phase high-performance liquid chromatography (RP-HPLC), matrix-assisted laser desorption ionisation-time of flight (MALDI-TOF) mass spectrometry and liquid chromatography electrospray ionisation mass spectrometry (LC-ESI-MS) to detect intraspecific variation, and the molecular weight data obtained with ESI-MS were used to assess toxin diversity. RP-HPLC and LC-ESI-MS/MS were used to characterise the venom proteome and estimate the relative abundances of protein families present. The most abundant protein family in January and June venoms is phospholipase A2 (PLA2: January 66.7%; June 54.5%), followed by three-finger toxins (3FTx: January 30.4%; June 40.4%) and a minor component of cysteine-rich secretory proteins (CRISP: January 2.5%; June 5%). Trace amounts of snake venom metalloproteinases (SVMP), C-type lectins and housekeeping and regulatory proteins were also found. Although the complexity of the venom is low by number of families present, each family contained a more diverse set of isoforms than previously reported, a finding that may have implications for the development of next-generation sea snake antivenoms. Intraspecific variability was shown to be minor with one obvious exception of a 14,157-Da protein that was present in some January (adult) venoms, but not at all in June (subadult) venoms. There is also a greater abundance of short-chain neurotoxins in June (subadult) venom compared with January (adult) venom. These differences potentially indicate the presence of seasonal, ontogenetic or sexual variation in H. curtus venom.
Highlights
The viviparous sea snakes (Elapidae: Hydrophiinae: Hydrophinii) consist of 62 species that are phylogenetically placed within the terrestrial elapids [1]
The spine-bellied sea snake (Hydrophis curtus; synonymous with Lapemis curtus, Lapemis hardwickii and Hydrophis hardwickii) [14], the most generalist feeder of all the sea snakes [4], is one of the species known to be responsible for human fatalities [15,16]
An estimate of the relative proportions of toxin families in H. curtus venom was attempted using cDNA cloned from venom gland mRNA, suggesting the venom contained 43.4% 3FTx, 9.8% phospholipase A2 (PLA2) and 2.3% cysteine-rich secretory proteins (CRISP) [28]
Summary
The viviparous sea snakes (Elapidae: Hydrophiinae: Hydrophinii) consist of 62 species that are phylogenetically placed within the terrestrial elapids [1]. The spine-bellied sea snake (Hydrophis curtus; synonymous with Lapemis curtus, Lapemis hardwickii and Hydrophis hardwickii) [14], the most generalist feeder of all the sea snakes [4], is one of the species known to be responsible for human fatalities [15,16] It is all the more hazardous because it is likely to be encountered by people, being one of the most widely-distributed sea snakes, found from northern Australia to the Persian Gulf via Southeast Asia [14], and is common throughout much of its range [12,15,17]. An estimate of the relative proportions of toxin families in H. curtus venom was attempted using cDNA cloned from venom gland mRNA, suggesting the venom contained 43.4% 3FTx, 9.8% PLA2 and 2.3% CRISP [28]. Intraspecific venom variation was assessed with RP-HPLC, matrix-assisted laser desorption ionisation-time of flight (MALDI-TOF) mass spectrometry and LC-ESI-MS, and toxin diversity was assessed using the data obtained with LC-ESI-MS
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