| Structural highlights
Function
[NXL1_NAJKA] The monomeric form binds with high affinity to muscular, Torpedo (muscle-type), and neuronal alpha-7 nicotinic acetylcholine receptors (nAChR). Has no effect on alpha-3/beta-2 nAChR. Causes paralysis by preventing acetylcholine binding to the nAChR. Does not show any blockade of the nicotine-evoked release of dopamine and does not affect ACh release. In mice lung cancer, causes reduction of tumor growth.[1] [2] [3] [4] [5] [6] [7] [8] [9] The homodimeric form binds with low affinity to Torpedo (muscle-type) and alpha-7 nAChRs, whereas it acquires the capacity to block alpha-3/beta-2 nAChRs.[10] [11] [12] [13] [14] [15] [16] [17] [18]
Publication Abstract from PubMed
In Naja kaouthia cobra venom, we have earlier discovered a covalent dimeric form of alpha-cobratoxin (alphaCT-alphaCT) with two intermolecular disulfides, but we could not determine their positions. Here, we report the alphaCT-alphaCT crystal structure at 1.94 A where intermolecular disulfides are identified between Cys(3) in one protomer and Cys(20) of the second, and vice versa. All remaining intramolecular disulfides, including the additional bridge between Cys(26) and Cys(30) in the central loops II, have the same positions as in monomeric alpha-cobratoxin. The three-finger fold is essentially preserved in each protomer, but the arrangement of the alphaCT-alphaCT dimer differs from those of noncovalent crystallographic dimers of three-finger toxins (TFT) or from the kappa-bungarotoxin solution structure. Selective reduction of Cys(26)-Cys(30) in one protomer does not affect the activity against the alpha7 nicotinic acetylcholine receptor (nAChR), whereas its reduction in both protomers almost prevents alpha7 nAChR recognition. On the contrary, reduction of one or both Cys(26)-Cys(30) disulfides in alphaCT-alphaCT considerably potentiates inhibition of the alpha3beta2 nAChR by the toxin. The heteromeric dimer of alpha-cobratoxin and cytotoxin has an activity similar to that of alphaCT-alphaCT against the alpha7 nAChR and is more active against alpha3beta2 nAChRs. Our results demonstrate that at least one Cys(26)-Cys(30) disulfide in covalent TFT dimers, similar to the monomeric TFTs, is essential for their recognition by alpha7 nAChR, although it is less important for interaction of covalent TFT dimers with the alpha3beta2 nAChR.
Dimeric alpha-cobratoxin X-ray structure: localization of intermolecular disulfides and possible mode of binding to nicotinic acetylcholine receptors.,Osipov AV, Rucktooa P, Kasheverov IE, Filkin SY, Starkov VG, Andreeva TV, Sixma TK, Bertrand D, Utkin YN, Tsetlin VI J Biol Chem. 2012 Feb 24;287(9):6725-34. Epub 2012 Jan 5. PMID:22223648[19]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Osipov AV, Kasheverov IE, Makarova YV, Starkov VG, Vorontsova OV, Ziganshin RKh, Andreeva TV, Serebryakova MV, Benoit A, Hogg RC, Bertrand D, Tsetlin VI, Utkin YN. Naturally occurring disulfide-bound dimers of three-fingered toxins: a paradigm for biological activity diversification. J Biol Chem. 2008 May 23;283(21):14571-80. Epub 2008 Apr 1. PMID:18381281 doi:http://dx.doi.org/M802085200
- ↑ Kang S, Maelicke A. Fluorescein isothiocyanate-labeled alpha-cobratoxin. Biochemical characterization and interaction with acetylcholine receptor from Electrophorus electricus. J Biol Chem. 1980 Aug 10;255(15):7326-32. PMID:6771288
- ↑ Martin BM, Chibber BA, Maelicke A. The sites of neurotoxicity in alpha-cobratoxin. J Biol Chem. 1983 Jul 25;258(14):8714-22. PMID:6553056
- ↑ Alkondon M, Albuquerque EX. alpha-Cobratoxin blocks the nicotinic acetylcholine receptor in rat hippocampal neurons. Eur J Pharmacol. 1990 Dec 4;191(3):505-6. PMID:2086254
- ↑ Apel C, Ricny J, Wagner G, Wessler I. alpha-Bungarotoxin, kappa-bungarotoxin, alpha-cobratoxin and erabutoxin-b do not affect [3H]acetylcholine release from the rat isolated left hemidiaphragm. Naunyn Schmiedebergs Arch Pharmacol. 1995 Dec;352(6):646-52. PMID:9053737
- ↑ Servent D, Winckler-Dietrich V, Hu HY, Kessler P, Drevet P, Bertrand D, Menez A. Only snake curaremimetic toxins with a fifth disulfide bond have high affinity for the neuronal alpha7 nicotinic receptor. J Biol Chem. 1997 Sep 26;272(39):24279-86. PMID:9305882
- ↑ Dajas-Bailador F, Costa G, Dajas F, Emmett S. Effects of alpha-erabutoxin, alpha-bungarotoxin, alpha-cobratoxin and fasciculin on the nicotine-evoked release of dopamine in the rat striatum in vivo. Neurochem Int. 1998 Oct;33(4):307-12. PMID:9840221
- ↑ Antil S, Servent D, Menez A. Variability among the sites by which curaremimetic toxins bind to torpedo acetylcholine receptor, as revealed by identification of the functional residues of alpha-cobratoxin. J Biol Chem. 1999 Dec 3;274(49):34851-8. PMID:10574958
- ↑ Grozio A, Paleari L, Catassi A, Servent D, Cilli M, Piccardi F, Paganuzzi M, Cesario A, Granone P, Mourier G, Russo P. Natural agents targeting the alpha7-nicotinic-receptor in NSCLC: a promising prospective in anti-cancer drug development. Int J Cancer. 2008 Apr 15;122(8):1911-5. PMID:18067132 doi:http://dx.doi.org/10.1002/ijc.23298
- ↑ Osipov AV, Kasheverov IE, Makarova YV, Starkov VG, Vorontsova OV, Ziganshin RKh, Andreeva TV, Serebryakova MV, Benoit A, Hogg RC, Bertrand D, Tsetlin VI, Utkin YN. Naturally occurring disulfide-bound dimers of three-fingered toxins: a paradigm for biological activity diversification. J Biol Chem. 2008 May 23;283(21):14571-80. Epub 2008 Apr 1. PMID:18381281 doi:http://dx.doi.org/M802085200
- ↑ Kang S, Maelicke A. Fluorescein isothiocyanate-labeled alpha-cobratoxin. Biochemical characterization and interaction with acetylcholine receptor from Electrophorus electricus. J Biol Chem. 1980 Aug 10;255(15):7326-32. PMID:6771288
- ↑ Martin BM, Chibber BA, Maelicke A. The sites of neurotoxicity in alpha-cobratoxin. J Biol Chem. 1983 Jul 25;258(14):8714-22. PMID:6553056
- ↑ Alkondon M, Albuquerque EX. alpha-Cobratoxin blocks the nicotinic acetylcholine receptor in rat hippocampal neurons. Eur J Pharmacol. 1990 Dec 4;191(3):505-6. PMID:2086254
- ↑ Apel C, Ricny J, Wagner G, Wessler I. alpha-Bungarotoxin, kappa-bungarotoxin, alpha-cobratoxin and erabutoxin-b do not affect [3H]acetylcholine release from the rat isolated left hemidiaphragm. Naunyn Schmiedebergs Arch Pharmacol. 1995 Dec;352(6):646-52. PMID:9053737
- ↑ Servent D, Winckler-Dietrich V, Hu HY, Kessler P, Drevet P, Bertrand D, Menez A. Only snake curaremimetic toxins with a fifth disulfide bond have high affinity for the neuronal alpha7 nicotinic receptor. J Biol Chem. 1997 Sep 26;272(39):24279-86. PMID:9305882
- ↑ Dajas-Bailador F, Costa G, Dajas F, Emmett S. Effects of alpha-erabutoxin, alpha-bungarotoxin, alpha-cobratoxin and fasciculin on the nicotine-evoked release of dopamine in the rat striatum in vivo. Neurochem Int. 1998 Oct;33(4):307-12. PMID:9840221
- ↑ Antil S, Servent D, Menez A. Variability among the sites by which curaremimetic toxins bind to torpedo acetylcholine receptor, as revealed by identification of the functional residues of alpha-cobratoxin. J Biol Chem. 1999 Dec 3;274(49):34851-8. PMID:10574958
- ↑ Grozio A, Paleari L, Catassi A, Servent D, Cilli M, Piccardi F, Paganuzzi M, Cesario A, Granone P, Mourier G, Russo P. Natural agents targeting the alpha7-nicotinic-receptor in NSCLC: a promising prospective in anti-cancer drug development. Int J Cancer. 2008 Apr 15;122(8):1911-5. PMID:18067132 doi:http://dx.doi.org/10.1002/ijc.23298
- ↑ Osipov AV, Rucktooa P, Kasheverov IE, Filkin SY, Starkov VG, Andreeva TV, Sixma TK, Bertrand D, Utkin YN, Tsetlin VI. Dimeric alpha-cobratoxin X-ray structure: localization of intermolecular disulfides and possible mode of binding to nicotinic acetylcholine receptors. J Biol Chem. 2012 Feb 24;287(9):6725-34. Epub 2012 Jan 5. PMID:22223648 doi:10.1074/jbc.M111.322313
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