Chemical modification of tryptophan residues in α-neurotoxins fromOphiophagus hannah (king cobra) venom

Chang, Chun-Chang; Lin, Pai-Mei; Chang, Long‐Sen; Kuo, Kou‐Wha

doi:10.1007/bf01888366

Cited by 8 publications

(5 citation statements)

References 23 publications

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“…The indole ring of this conserved tryptophan is exposed to the solvent. Modification of Trp 27 in a long neurotoxin analogue (Oh-4) from the king cobra venom showed a significant loss in the toxicity and acetylcholine binding efficiency of the toxin (37). Lys 24 is yet another residue that is well conserved among the neurotoxins (5,6).…”

Section: Discussionmentioning

confidence: 99%

Solution Structure of Toxin b, a Long Neurotoxin from the Venom of the King Cobra (Ophiophagus hannah)

Peng

Kumar

Jayaraman

et al. 1997

Journal of Biological Chemistry

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The solution structure of toxin b, a long neurotoxin (73 amino acids and 5 disulfides) from the venom of Ophiophagus hannah (king cobra), has been determined using 1 H NMR and dynamical simulated annealing techniques. The structures were calculated using 485 distance constraints and 52 dihedral angle restraints. The 21 structures that were obtained satisfy the experimental restraints and possess good nonbonded contacts. Analysis of the converged structures revealed that the protein consists of a core region from which three finger-like loops extend outwards. The regular secondary structure in toxin b includes a double and a triple stranded antiparallel ␤ sheet. Comparison with the solution structures of other long neurotoxins reveals that although the structure of toxin b is similar to those of previously reported long neurotoxins, clear local structural differences are observed in regions proposed to be involved in binding to the acetylcholine receptor. A positively charged cluster is found in the C-terminal tail, in Loop III, and in the tip of Loop II. This cationic cluster could be crucial for the binding of the long neurotoxins to the acetylcholine receptor.Venom of snakes from the Elapidae and Hydrophyidae families possesses proteins with pronounced pharmacological activities (1, 2). Some of these proteins are potent cardiotoxins (3, 4), whereas others are postsynaptic neurotoxins (5-7). The neurotoxins are classified into two general groups, long and short neurotoxins (8,9). Both classes of toxins bind specifically to the nicotinic acetylcholine receptor and block synaptic nerve transmission (10, 11). Binding of the neurotoxins to the acetylcholine receptor leads to a complete closure of the channel (11). The extremely tight, noncovalent association between the receptor and neurotoxins (K d ranging from 10 Ϫ9 to 10 Ϫ11 M) in comparison with that of acetylcholine (K d of 10 Ϫ6 M) makes them useful tools with which to investigate the function of the neuromuscular synapse and its receptors (10, 12). The long and short neurotoxins exhibit sequence homology and similar overall topologies, characterized by a three stranded antiparallel ␤ sheet and three finger-like loops protruding from a globular core (13). Long neurotoxins have four disulfide bridges like the short neurotoxins but possess an additional disulfide bridge in the central loop of the molecule. In addition to insertion and deletion within the main chain itself, long neurotoxins have an extra polypeptide chain between residues 65 and 73 that gives rise to a characteristic C-terminal tail (2). In long neurotoxins, the least conserved regions tend to be found in the C-terminal tail and the first loop (9). To date, x-ray and NMR structures of three long neurotoxins, namely ␣-cobratoxin (14, 15), ␣-bungarotoxin (16), and LSIII from Laticauda semifasciata (17), have been determined. The king cobra (Ophiophagus hannah), which belongs to the elapid family, is the world's largest poisonous snake (18). At least six long neurotoxin isoforms have been isolated ...

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Section: Discussionmentioning

confidence: 99%

Solution Structure of Toxin b, a Long Neurotoxin from the Venom of the King Cobra (Ophiophagus hannah)

Peng

Kumar

Jayaraman

et al. 1997

Journal of Biological Chemistry

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“…Furthermore, a chemical modification study indicated the importance of tryptophan residue for toxicity of DNTx‐III (Figure B). Among the many amino acid residues in neurotoxins, tryptophan was found to be important for its function; modification of this residue resulted in the complete loss of its acetylcholine receptor‐binding activity and a decreased toxic effect . The chemically modified as well as unmodified DNTx‐III gave a single sharp band in Western blot (Figure D), suggesting that modified toxin is structurally intact.…”

Section: Discussionmentioning

confidence: 99%

Purification, Characterization, and Chemical Modification of Neurotoxic Peptide from Daboia russelii Snake Venom of India

Venkatesh

Prasad

Sing

et al. 2013

J Biochem & Molecular Tox

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Comprehensive knowledge of venom composition is very important for effective management of snake envenomation and antivenom preparation. Daboia russelii venom from the eastern region of India is the most neurotoxic among the four venom samples investigated. From the eastern D. russelii venom sample, neurotoxic peptide has been purified by combined method of ion exchange gel permeation chromatography and reversed phase high performance liquid chromatography. Molecular weight of Daboia neurotoxin III (DNTx-III) found to be 6,849 Da (as measured on matrix-assisted laser desorption/ionisation-time of flight mass spectrometer), and N-terminal amino acid sequences is I K C F I T P D U T S Q A. Approximate LD50 dosage was 0.24 mg/kg body weight. It produced concentration- and time-dependent inhibition of indirectly stimulated twitches of Rana hexadactyla sciatic nerve gastrocnemius muscle preparations. Chemical modification of DNTx-III tryptophan residue(s) reduced the twitch height inhibition property of toxin, signifying the importance of tryptophan residues for the neurotoxic function. This type of neurotoxic peptide is unique to east Indian regional D. russelii venom.

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“…Although several α-neurotoxins have been previously isolated from O. hannah venom to study their protein structure (Lin et al, 1995a;Lin et al, 1995b;Chang et al, 1995;Lin et al, 1997;Chang et al, 2000;Roy et al, 2010), there is a need for pharmacological studies to characterize the main neurotoxins that potentially contribute to human neuromuscular paralysis. This study aimed to isolate the main neurotoxins from O. hannah venom and identify the mode of action, as well as determine the in vitro efficacy of Thai Red Cross Society King Cobra antivenom in neutralizing them.…”

Section: Introductionmentioning

confidence: 99%

Isolation and Pharmacological Characterization of α-Elapitoxin-Oh3a, a Long-Chain Post-Synaptic Neurotoxin From King Cobra (Ophiophagus hannah) Venom

et al. 2022

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The King Cobra (Ophiophagus hannah) is the world’s largest venomous snake and has a widespread geographical distribution throughout Southeast Asia. Despite proteomic studies indicating the presence of postsynaptic neurotoxins in O. hannah venom, there are few pharmacological investigations of these toxins. We isolated and characterized α-elapitoxin-Oh3a (α-EPTX-Oh3a; 7,938 Da), a long-chain postsynaptic neurotoxin, which constitutes 5% of O. hannah venom. α-EPTX-Oh3a (100–300 nM) caused concentration-dependent inhibition of indirect twitches and inhibited contractile responses of tissues to exogenous acetylcholine and carbachol, in the chick biventer cervicis nerve-muscle preparation. The prior incubation of tissues with Thai Red Cross Society King Cobra antivenom (1 ml/0.8 mg) prevented the in vitro neurotoxic effects of α-EPTX-Oh3a (100 nM). The addition of Thai Red Cross Society King Cobra antivenom (1 ml/0.8 mg), at the t90 time point partially reversed the in vitro neurotoxicity of α-EPTX-Oh3a (100 nM). Repeatedly washing the tissue did not allow significant recovery from the in vitro neurotoxic effects of α-EPTX-Oh3a (100 nM). α-EPTX-Oh3a demonstrated pseudo-irreversible antagonism of concentration-response curves to carbachol, with a pA2 of 8.99. De novo sequencing of α-EPTX-Oh3a showed a long-chain postsynaptic neurotoxin with 72 amino acids, sharing 100% sequence identity with Long neurotoxin OH-55. In conclusion, the antivenom is useful for reversing the clinically important long-chain α-neurotoxin-mediated neuromuscular paralysis.

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Chemical modification of tryptophan residues in α-neurotoxins fromOphiophagus hannah (king cobra) venom

Cited by 8 publications

References 23 publications

Solution Structure of Toxin b, a Long Neurotoxin from the Venom of the King Cobra (Ophiophagus hannah)

Solution Structure of Toxin b, a Long Neurotoxin from the Venom of the King Cobra (Ophiophagus hannah)

Purification, Characterization, and Chemical Modification of Neurotoxic Peptide from Daboia russelii Snake Venom of India

Isolation and Pharmacological Characterization of α-Elapitoxin-Oh3a, a Long-Chain Post-Synaptic Neurotoxin From King Cobra (Ophiophagus hannah) Venom

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