Background:
Conus amadis is a carnivorous snail found abundantly in coastal waters of
India. Despite its abundance in southern coastal waters of India and the fact that most of the
conotoxin act in neuronal system, research work on Conus amadis venom was not much focused.
So we have made a brief study on the venom complex of Conus amadis to identify the library of
novel conotoxins and to screen the natural venom for neurological function.
Objective:
De novo sequencing of novel conopeptides from the venom cocktail of Conus amadis
and to screen its natural venom for the presence of biological activities in zebrafish model.
Methods:
Proteome based MALDI-TOF and LC-MS-MS analysis for identification of novel
conotoxins and subsequent sequencing. Due to the complex disulfide rich nature of the venom
peptides, the study also involves global chemical modification experiments of the venom extract to
unambiguously determine the sequence of novel conotoxins. Biological function analysis of natural
venom was tested in zebrafish model to ascertain anti-epileptic properties.
Results:
In this study, we have identified 19 novel conotoxins containing 1, 2 & 3 disulfides,
belonging to different classes. Among them, 2 novel contryphans, 3 T-superfamily conotoxins, 2
A-superfamily conotoxins and 2 Mini M-Superfamily conotoxins were sequenced to its amino acid
level from the fragmented spectrum of singly and doubly charged parent ions using de novo
sequencing strategies. ama1054, a contryphan peptide toxin, possesses post translationally modified
bromo tryptophan at its seventh position. Except ama1251, all the sequenced peptide toxins possess
modified C-terminal amidation. Crude venom exhibited anticonvulsant properties in
pentylenetetrazole-induced seizure in zebrafish larvae, which suggested anti-epileptic property of
the venom cocktail. Acetylcholinesterase activity was also identified in the venom complex.
Conclusion:
Based on the preliminary evidence, if this study is extended further through bioassay
guided purification, could possibly yield peptide toxins with anticonvulsant and other
neurologically active molecules.
A survey of the marine gastropod genus Conus Linnaeus was conducted along the TamilNadu Coast of India to explore the regional geographic distribution and diversity. The 60 species observed increased the number of Indian Conidae from 77 to 81. Conus imperialis Linné, C. mitratus Hwass in Bruguière, C. striolatus Kiener and C. violaceus Gmelin are newly recorded from the study area. Conus amadis Gmelin was the most widely distributed species. The highest diversity (48 species) occurred in the Gulf of Mannar, followed by 22 species from northern, six from southern, and five from the Palk Bay regions. We suggest that the rich diversity recorded in the Gulf of Mannar reflects the physical conditions, microhabitats and required resources such as food and shelter that favour the occurrence of the large number of Conus species.
The occurrence of contryphans, a class of single-disulfide-bond-containing peptides, is demonstrated by the analysis of the venom of nine species of cone snails. Ten full gene sequences and two partial gene sequences coding for contryphan precursor proteins have been identified by next-generation sequencing and compared with available sequences. The occurrence of mature peptides in isolated venom has been demonstrated by LC-ESI-MS/MS analysis. De novo sequencing of reduced, alkylated contryphans from C. frigidus and C. araneosus provides evidence of sequence variation and post-translational modification, notably gamma carboxylation of glutamic acid. The characterization of Fr965 (C. frigidus) provides a rare example of a sequence lacking Pro at position 5 in the disulfide loop. The widespread occurrence of contryphan genes and mature peptides in the venom of diverse cone snails is suggestive of their potential biological significance.
The Andaman and Nicobar archipelago comprises 572 islands spread over an area of 8,249 sq. km. These islands are within the 'Indo-Malayan region' and near the 'faunistic centre' from which other Indo-West Pacific regions recruit their tropical marine fauna (Ekman, 1953). The topographically complex nature of the nearshore environments of these islands creates a plethora of niches that support a rich and diverse molluscan fauna. Many of the Conus species (e.g., C. geographus Linnaeus, 1758; C. miles Linnaeus, 1758; and C. striatus Linnaeus, 1758) that occupy these islands are broadly distributed throughout the Indo-West Pacific. However, a few Indo-West Pacific species (e.g., Conus andamanensis Smith, 1878; and C. araneosus nicobaricus Hwass in Bruguière, 1792) are restricted to small geographic regions (Röckel et. al. 1995). Early oceanographic expeditions of the Andaman and Nicobar Islands that began in 1788 report only 10 Conus species from these islands (Smith, 1878; Melvill & Sykes, 1898; Preston, 1908). More recently, Subba Rao (1980) of the Zoological Survey of India (ZSI) reports a total of 51 Conus species from this region. In the past two decades, the Conus fauna has not been studied extensively due to lack of focused studies in the Andaman andNicobar Islands. Several recent surveys conducted by the Andaman and Nicobar Centre for Ocean Science and Technology investigated the intertidal and subtidal macrobenthic fauna of theAndaman Islands.
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