Whittington CM et al. (2010), Novel venom gene discovery in the platypus.

ECB-ART-41784

Genome Biol 2010 Jan 01;119:R95. doi: 10.1186/gb-2010-11-9-r95.

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Novel venom gene discovery in the platypus.

Whittington CM , Papenfuss AT , Locke DP , Mardis ER , Wilson RK , Abubucker S , Mitreva M , Wong ES , Hsu AL , Kuchel PW , Belov K , Warren WC .

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BACKGROUND: To date, few peptides in the complex mixture of platypus venom have been identified and sequenced, in part due to the limited amounts of platypus venom available to study. We have constructed and sequenced a cDNA library from an active platypus venom gland to identify the remaining components. RESULTS: We identified 83 novel putative platypus venom genes from 13 toxin families, which are homologous to known toxins from a wide range of vertebrates (fish, reptiles, insectivores) and invertebrates (spiders, sea anemones, starfish). A number of these are expressed in tissues other than the venom gland, and at least three of these families (those with homology to toxins from distant invertebrates) may play non-toxin roles. Thus, further functional testing is required to confirm venom activity. However, the presence of similar putative toxins in such widely divergent species provides further evidence for the hypothesis that there are certain protein families that are selected preferentially during evolution to become venom peptides. We have also used homology with known proteins to speculate on the contributions of each venom component to the symptoms of platypus envenomation. CONCLUSIONS: This study represents a step towards fully characterizing the first mammal venom transcriptome. We have found similarities between putative platypus toxins and those of a number of unrelated species, providing insight into the evolution of mammalian venom.

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Genes referenced: LOC100887844 LOC578116 LOC578975 LOC752081 LOC756768

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	Figure 1. Representation of the putative platypus venom gene families discovered by homology searching with other toxin sequences. Putative functions are shown in Table 1.
	Figure 2. Gene Ontology annotation of putative platypus venom genes. (a) Biological process; (b) cellular component; (c) molecular function. Data can be classified under more than one GO term.
	Figure 3. Partial MUSCLE alignment of putative platypus venom kallikrein serine protease sequences, showing the most conserved regions. The full alignment can be seen in Figure S5 in Additional file 1. Gilatoxin (P43685), blarina toxin (BAD18893), blarinasin (Q5FBW2), two snake sequences and two human tissue kallikreins are also shown (SWISS-PROT accession numbers are listed). The catalytic triad is highlighted in pink, and conserved cysteines highlighted in blue. Not all platypus venom peptides contain the triad and cysteines.
	Figure 4. Representation of domain order in the platypus venom metalloproteinases for which we appear to have complete sequence. Lowercase h denotes that the residue is not found in all platypus sequences. This arrangement mirrors that of the snake venom PIII metalloproteinases (after Matsui et al. [28]). Domains were identified using BLAST searches of the NCBI Conserved Domains database [66].
	Figure 5. Unrooted neighbor-joining phylogenetic tree of the kunitz domain-containing putative platypus venom peptides (boxed). Bootstrap values less than 50 have been omitted. ENSOANT represents platypus homologues not expressed in venom gland.

References [+] :

Anderluh, Cytolytic peptide and protein toxins from sea anemones (Anthozoa: Actiniaria). 2002, Pubmed