Coralsnake venomics: analyses of venom gland transcriptomes and proteomes of six brazilian taxa
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2017
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Venom gland transcriptomes and proteomes of six Micrurus taxa (M. corallinus,
M. lemniscatus carvalhoi, M. lemniscatus lemniscatus, M. paraensis, M. spixii spixii, and M. surinamensis)
were investigated, providing the most comprehensive, quantitative data on Micrurus venom
composition to date, and more than tripling the number of Micrurus venom protein sequences
previously available. The six venomes differ dramatically. All are dominated by 2–6 toxin classes
that account for 91–99% of the toxin transcripts. The M. s. spixii venome is compositionally the
simplest. In it, three-finger toxins (3FTxs) and phospholipases A2 (PLA2s) comprise >99% of the toxin
transcripts, which include only four additional toxin families at levels 0.1%. Micrurus l. lemniscatus
venom is the most complex, with at least 17 toxin families. However, in each venome, multiple
structural subclasses of 3FTXs and PLA2s are present. These almost certainly differ in pharmacology
as well. All venoms also contain phospholipase B and vascular endothelial growth factors. Minor
components (0.1–2.0%) are found in all venoms except that of M. s. spixii. Other toxin families are
present in all six venoms at trace levels (<0.005%). Minor and trace venom components differ in each
venom. Numerous novel toxin chemistries include 3FTxs with previously unknown 8- and 10-cysteine
arrangements, resulting in new 3D structures and target specificities. 9-cysteine toxins raise the
possibility of covalent, homodimeric 3FTxs or heterodimeric toxins with unknown pharmacologies.
Probable muscarinic sequences may be reptile-specific homologs that promote hypotension via
vascular mAChRs. The first complete sequences are presented for 3FTxs putatively responsible for
liberating glutamate from rat brain synaptosomes. Micrurus C-type lectin-like proteins may have
6–9 cysteine residues and may be monomers, or homo- or heterodimers of unknown pharmacology.
Novel KSPIs, 3 longer than any seen previously, appear to have arisen in three species by gene
duplication and fusion. Four species have transcripts homologous to the nociceptive toxin, (MitTx)
-subunit, but all six species had homologs to the -subunit. The first non-neurotoxic, non-catalytic
elapid phospholipase A2s are reported. All are probably myonecrotic. Phylogenetic analysis indicates
that the six taxa diverged 15–35 million years ago and that they split from their last common ancestor with Old World elapines nearly 55 million years ago. Given their early diversification, many cryptic
micrurine taxa are anticipated.
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Coralsnakes, Molecular models, Micrurus, Novel toxins, Phospholipase A2, Venom gland transcriptomes, Proteomes, 3FTx
Citação
AIRD, Steven D. et al. Coralsnake venomics: analyses of venom gland transcriptomes and proteomes of six brazilian taxa. Toxins, Basel, v. 9, n. 6, 2017. DOI: 10.3390/toxins9060187. Disponível em: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5488037/. Acesso em: 27 jan. 2023.