| 词条 | Covalitoxin-II |
| 释义 |
Covalitoxin-II is a peptide toxin that is produced by the spider Coremiocnemis validus. It can induce excitatory, non-lethal behavioral symptoms like quivering and jerking in crickets. SourcesCovalitoxin-II (Cvtx-II) is a toxin in the venom of Coremiocnemis validus (Singapore or Blue femur tarantula).[1][1] This spider lives in South East Asian tropical forests.[1] ChemistryStructureThe toxin consists of 31 amino acids (ACSRAGENCYKSGRCCDGLYCKAYVVTCYKP). This sequence forms a peptide with a molecular weight of 3.4 kDa. It has six cysteine residues which form three disulphide bonds, between the specific amino acid locations 2&16, 19&21 and 15&28.[1] There is an equal distribution of hydrophilic, hydrophobic and neutral amino acids. Near the C-terminus there is a positively charged surface formed by conserved basic residues, which is thought to interact with an ion channel.[2][3] The inhibitor cystine knot motif that is formed by the cysteine residues shows analogy to other spider toxins and can also be found in ω-conotoxins, which are present in the venom of cone snails. It has low homology with two peptides:
Target and mode of actionThe specific target and mode of action of Cvtx-II are not yet clear. Based on its effect on behavior, it has been speculated that Cvtx-II targets sodium channel inactivation, analogous to some excitotoxins.[2] ToxicityCvtx-II induces the following non-lethal symptoms in crickets:
Experiments have shown that these symptoms are not in present in cockroaches or mice after Cvtx-II injections. Therefore, Cvtx-II is thought to be an insect species-specific neurotoxic peptide. A dose of 0.2 µmol/g was necessary to immobilize or inactivate 50% of the insects (ID50). After 40–60 minutes, the immobilizing effects disappear.[2] References1. ^1 UniProt, UniProt Knowledge Base; P82601 (TXVL2_CORVA); published December 1, 2000; Last modified October 3, 2012; Date of retrieval October 16, 2012; 2. ^1 2 3 4 5 {{cite journal |vauthors=Balaji RA, Sasaki T, Gopalakrishnakone P, Sato K, Kini RM, Bay BH |title=Purification, structure determination and synthesis of covalitoxin-II, a short insect-specific neurotoxic peptide from the venom of the Coremiocnemis validus (Singapore tarantula) |journal=FEBS Lett. |volume=474 |issue=2-3 |pages=208–12 |year=2000 |pmid=10838086 |doi= 10.1016/s0014-5793(00)01593-3}} 3. ^Grishin E; Polypeptide neurotoxins from spider venoms; Eur. J. Biochem. 1999 Sep;264(2):276-80. {{Cite journal | doi = 10.1046/j.1432-1327.1999.00622.x | last1 = Grishin | first1 = E. | title = Polypeptide neurotoxins from spider venoms | journal = European Journal of Biochemistry / FEBS | volume = 264 | issue = 2 | pages = 276–280 | year = 1999 | pmid = 10491071}} 1 : Invertebrate toxins |
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