| 词条 | Halcurin |
| 释义 |
Source and etymologyThe polypeptide toxin halcurin is named after its source: the sea anemone genus Halcurias,[1] which are ocean dwelling solitary invertebrates.[2] ChemistryThe amino acid sequence of halcurin is: VACRCESDGP DVRSATFTGT VDLWNCNTGW HKCIATYTAV ASCCKKD; it consists of 47 amino acids and has a molecular weight of 5,086 Da [1] General informationA classification of sea anemone polypeptide neurotoxins has been proposed based on their amino acid sequence, dividing the group into three classes of sodium channel toxins.[3] Halcurin is structurally homologous with type 2 toxins, but also has sequence homology to type 1 toxins.[1] Type 1 and 2 toxins are composed of 46 to 49 amino acid residues, and cross-linked by three disulfide bridges.[2] Ten residues including six Cysteine (Cys) residues are completely conserved between type 1 and 2 toxins.[3] Therefore, it is possible that type 1 and 2 toxins have evolved from Halcurin as a common ancestor.[1] TargetType 1 and 2 toxins are known to target neurotoxin receptor site 3.[4] Based on the structural homology of halcurin with sea anemone toxin type 1 and 2 [1] it is likely to target neurotoxin receptor site 3. Neurotoxin receptor site 3 is predicted to be at the domain IV of voltage gated sodium channel, more specifically at the extracellular loop of segment 3-4. These voltage gated sodium channels are found in neurons, skeletal muscles, and cardiac muscles.[2]Mode of actionThe domain III and IV intracellular loop structure acts as a fast inactivation gate in voltage gated sodium channels.[5] Sea anemone toxin type 1 and 2 slow or prevent the conformational changes in domain IV segment 3-4 loop required for inactivation of the channel.[6] Based on the structural homology of halcurin to sea anemone neurotoxin type 1 and 2,[1] it is likely to have a similar mode of action. ToxicityHalcurin has a median lethal dose (LD50) of 5.8 µg /kg for crabs, but it does not show lethality in mice.[1] References1. ^1 2 3 4 5 6 7 8 {{cite journal | last1 = Ishida | first1 =M | title = Halcurin, a polypeptide toxin in the sea anemone Halcurias sp., with a structural resemblance to type 1 and 2 toxins | journal = Toxicon | volume = 35 | pages = 537–544 |pmid= 9133708 | issue=4 |date=Apr 1997 | doi=10.1016/s0041-0101(96)00143-2}} 2. ^1 2 {{cite journal | last1 = Bosmans | first1 =F | title = The sea anemone Bunodosoma granulifera contains surprisingly efficacious and potent insect-selective toxins | journal = FEBS | volume = 532 | pages = 131–134 |pmid= 12459477 | issue=1-2 |date=Dec 2002 | doi=10.1016/s0014-5793(02)03653-0}} 3. ^1 {{cite journal | last1 = Norton | first1 =RS | title = Structure and structure-function relationships of sea anemone proteins that interact with the sodium channel | journal = Toxicon | volume = 29 | pages = 1051–1084 |pmid= 1686683 | doi=10.1016/0041-0101(91)90205-6 | year=1991}} 4. ^{{cite journal |last1=Honma |first1=Tomohiro |last2=Shiomi |first2=Kazuo |title=Peptide Toxins in Sea Anemones: Structural and Functional Aspects |journal=Marine Biotechnology |volume=8 |issue=1 |pages=1–10 |year=2006 |pmid=16372161 |doi=10.1007/s10126-005-5093-2 |pmc=4271777}} 5. ^{{cite journal | last1 = Caterall | first1 =WA | title = Structure and function of voltage-gated ion channels | journal = Annual Review of Biochemistry | volume = 64 | pages = 493–531 |pmid= 7574491 | doi=10.1146/annurev.bi.64.070195.002425 | year=1995}} 6. ^{{cite journal | last1 = Rogers | first1 =JC | title = Molecular determinants of high affinity binding of alpha-scorpion toxin and sea anemone toxin in the S3-S4 extracellular loop in domain IV of the Na+ channel alpha subunit | journal = Journal of Biological Chemistry | volume = 271 | pages = 15950–15962 |pmid= 8663157 | issue=27 |date=Jul 1996 | doi=10.1074/jbc.271.27.15950}} External links
3 : Neurotoxins|Ion channel toxins|Invertebrate toxins |
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