Draft:Av3
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Submission declined on 14 November 2025 by WeirdNAnnoyed (talk).
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Comment: I'm not convinced this compound is notable per usual standards because all sources cited (as far as I can tell) are primary. If secondary sources can be found then cite them and we can reconsider. Also, the article needs some cleanup. Please use the Greek characters rather than "a-helix" and "f-sheet" (these can be found under "special characters" in the editing window). The last section (Treatment) is unsourced; either provide a citation or remove this part. WeirdNAnnoyed (talk) 12:13, 14 November 2025 (UTC)
| Molecular formula | C125H171N35O36S6 |
|---|---|
| Number of atoms | 202 |
| Molecular mass | 2.94 kDa |
| pI | 8.1 |
| Amino acid sequence (27 residues) | R S C C P C Y W G G C P W G Q N C Y P E G S C G P K V |
| Modifications | Disulfide bonds: 3-17, 4-11, 6-22 |
Av3
[edit]Av3 (also: ATX III, Delta-actitoxin-Avd2a, Delta-AITX-AVd2a, neurotoxin 3) is a 27-residue polypeptide neurotoxin produced by Anemonia viridis (also Anemonia sulcata). Av3 produces neurotoxic symptoms in crustaceans by reducing sodium channel inactivation, which prolongs the action potential in excitable tissues.
Etymology
[edit]Av3 is an abbreviation from Anemonia viridis toxin 3. Originally Av3 was called ATX-III, which is an acronym for Anemonia sulcata toxin 3. In recent literature, researchers use the species name Anemonia viridis as a synonym for Anemonia sulcata and use the abbreviation Av3 to refer to the neurotoxin [1][2][3][4], whether Anemonia viridis and Anemonia sulcata should be recognized as synonyms remains a matter of dispute.[5]
Source
[edit]Av3 is isolated from the venom of the sea anemones Anemonia viridis and Anemonia sulcata. Av3 was the third toxin isolated from the venom of Anemonia sulcata, the first and second being ATX-I and ATX-II.[6]
Chemistry
[edit]Av3 is a small neurotoxin consisting of 27 amino acids stabilized by three disulfide bridges.[2] The polypeptide contains no regular α-helix or β-sheet and instead consists of a network of reverse turns.[7] The molecule can be divided into three regions: a polar N-terminal dipeptide, a predominantly hydrophobic central region (residues 3-14), and a polar C-terminal segment.[8]
Av3 is structurally unique compared to bioactive surfaces of toxins with a similar target and consists mainly of aromatic residues as well as glycine residues. Glycine residues make up nearly 20% of the total amino acid content.[2][8]
Target
[edit]Av3 acts on invertebrate voltage-gated sodium channels (Nav).[4] Specifically, Av3 binds to a cleft in S6 of domain I [1] and likely also has contact with the S4 region of domain IV, which is proximal to the pore module of domain I.[3]
Av3 has an effect on sodium channels in insects, but not on mammalian sodium channels. [1][2][4]. At 10 µM, Av3 has no effect on the mammalian Nav subtypes: Nav1.2, Nav1.4, and Nav1.6, and a ‘negligible effect’ on mammalian subtype Nav1.5.[2] Another study also found that 10 µM Av3 had no effect on the Nav1.2a channel, while the toxin did inhibit Drosophila melanogaster DmNav1 inactivation.[1] A similar effect on sodium channel activity is also found for crayfish neurons.[9]
Competition binding assays demonstrate that Av3 competes with the scorpion α-toxin LqhαIT, which is known to bind site-3 on the extracellular region of the α-subunit of insect Navs, confirming the classification of Av3 as a site-3 toxin.[2]
Mode of action
[edit]Av3 selectively targets voltage-gated sodium channels (Nav) on the extracellular region of the α-subunit.[10] Through this interaction, the toxin functions as a gating modifier that inhibits the fast inactivation, increases peak sodium current at more negative membrane potentials, and shifts activation to lower voltages, resulting in a sustained inward sodium current and prolonged action potentials.[9]
The binding of Av3 is voltage dependent: depolarizing the membrane increases the toxin's dissociation rate from the channel, indicating stronger interactions with sodium channels in their resting and early open states than when they are strongly activated.[11] For example, the dissociation rate increases by approximately two orders of magnitude when the membrane potential is shifted from –100 mV to 0 mV.[11]
In crayfish neurons, it was found that Av3 shifts the voltage dependence of activation to more negative potentials, causing voltage channels to open earlier and neurons to become hyperexcitable.[9]
These combined effects initially lead to repetitive firing, but as depolarization persists and sodium channels fail to recover, action potential propagation is disrupted, consistent with the paralysis observed in crustaceans.[6][9]
Toxicity
[edit]Av3 produces neurotoxic symptoms in crustaceans, typically causing cramp-like reactions followed by paralysis of the extremities when injected into Carcinus maenas.[6] The toxicity reflects the toxin's high selectivity for invertebrate sodium channels.[1][2] Although the symptoms in arthropods are well described, quantitative LD50 data have not been reported. In contrast, i.p. LD50 in mice is greater than 18 mg/kg, indicating low toxicity in mammals.[12]
References
[edit]- ^ a b c d e Gur Barzilai, Maya; Kahn, Roy; Regev, Noa; Gordon, Dalia; Moran, Yehu; Gurevitz, Michael (2014-10-15). "The specificity of Av3 sea anemone toxin for arthropods is determined at linker DI/SS2–S6 in the pore module of target sodium channels". Biochemical Journal. 463 (2): 271–277. doi:10.1042/BJ20140576. ISSN 0264-6021. PMID 25055135.
- ^ a b c d e f g Moran, Yehu; Kahn, Roy; Cohen, Lior; Gur, Maya; Karbat, Izhar; Gordon, Dalia; Gurevitz, Michael (2007-08-15). "Molecular analysis of the sea anemone toxin Av3 reveals selectivity to insects and demonstrates the heterogeneity of receptor site-3 on voltage-gated Na+ channels". Biochemical Journal. 406 (1): 41–48. doi:10.1042/BJ20070233. ISSN 0264-6021. PMC 1948988. PMID 17492942.
- ^ a b Zhu, Qing; Du, Yuzhe; Nomura, Yoshiko; Gao, Rong; Cang, Zixuan; Wei, Guo-Wei; Gordon, Dalia; Gurevitz, Michael; Groome, James; Dong, Ke (2021-10-01). "Charge substitutions at the voltage-sensing module of domain III enhance actions of site-3 and site-4 toxins on an insect sodium channel". Insect Biochemistry and Molecular Biology. 137 103625. Bibcode:2021IBMB..13703625Z. doi:10.1016/j.ibmb.2021.103625. ISSN 0965-1748. PMC 9376739. PMID 34358664.
- ^ a b c Moran, Yehu; Gordon, Dalia; Gurevitz, Michael (March 2009). "Sea anemone toxins affecting voltage-gated sodium channels – molecular and evolutionary features". Toxicon. 54 (8): 1089–1101. Bibcode:2009Txcn...54.1089M. doi:10.1016/j.toxicon.2009.02.028. PMC 2807626. PMID 19268682.
- ^ "WoRMS - World Register of Marine Species - Anemonia sulcata (Pennant, 1777)". www.marinespecies.org. Retrieved 2025-11-17.
- ^ a b c Béress, Lászlo; Béress, Rosemarie (1975). "Isolation and characterisation of three polypeptides with neurotoxic activity from Anemonia sulcata". FEBS Letters. 50 (3): 311–314. Bibcode:1975FEBSL..50..311B. doi:10.1016/0014-5793(75)90057-5. ISSN 1873-3468. PMID 234860.
- ^ Norton, R S; Cross, K; Braach-Maksvytis, V; Wachter, E (1993-07-15). "1H-n.m.r. study of the solution properties and secondary structure of neurotoxin III from the sea anemone Anemonia sulcata". Biochemical Journal. 293 (2): 545–551. doi:10.1042/bj2930545. ISSN 0264-6021. PMC 1134396. PMID 8102051.
- ^ a b Martinez, G.; Kopeyan, C. (1977). "Toxin III from Anemonia sulcata: Primary structure". FEBS Letters. 84 (2): 247–252. Bibcode:1977FEBSL..84..247M. doi:10.1016/0014-5793(77)80699-6. ISSN 1873-3468. PMID 23311.
- ^ a b c d Hartung, Klaus; Rathmayer, Werner (1985-05-01). "Anemonia sulcata toxins modify activation and inactivation of Na+ currents in a crayfish neurone". Pflügers Archiv. 404 (2): 119–125. doi:10.1007/BF00585406. ISSN 1432-2013. PMID 2409523.
- ^ Catterall, William A.; Cestèle, Sandrine; Yarov-Yarovoy, Vladimir; Yu, Frank H.; Konoki, Keiichi; Scheuer, Todd (February 2007). "Voltage-gated ion channels and gating modifier toxins". Toxicon. 49 (2): 124–141. Bibcode:2007Txcn...49..124C. doi:10.1016/j.toxicon.2006.09.022. PMID 17239913.
- ^ a b Warashina, Akira; Jiang, Zheng-Yao; Ogura, Tatsuya (1988-01-01). "Potential-dependent action of Anemonia sulcata toxins III and IV on sodium channels in crayfish giant axons". Pflügers Archiv. 411 (1): 88–93. doi:10.1007/BF00581651. ISSN 1432-2013. PMID 2451216.
- ^ Schweitz, Hugues (1984-01-01). "Lethal potency in mice of toxins from scorpion, sea anemone, snake and bee venoms following intraperitoneal and intracisternal injection". Toxicon. 22 (2): 308–311. Bibcode:1984Txcn...22..308S. doi:10.1016/0041-0101(84)90032-1. ISSN 0041-0101. PMID 6145236.
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