Neurotoxin cobra

Since the rate constants of bimolecular diffusion-limited reactions in isotropic solution are proportional to T/ these data testify to the fact that the kt values are linearly dependent on the diffusion coefficient D in water, irrespective of whether the fluorophores are present on the surface of the macromolecule (human serum albumin, cobra neurotoxins, proteins A and B of the neurotoxic complex of venom) or are localized within the protein matrix (ribonuclease C2, azurin, L-asparaginase).1 36 1 The linear dependence of the functions l/Q and l/xF on x/t] indicates that the mobility of protein structures is correlated with the motions of solvent molecules, and this correlation results in similar mechanisms of quenching for both surface and interior sites of the macromolecule. 

Toxin-agglutinin fold Erabutoxin, cobra neurotoxin... 

In the elapids, the group that includes the cobra, a toxin acting on nerves and muscles, a neurotoxin, is responsible for the death of the victim. It causes paralysis of breathing (see box). In addition, the victim will show speech incoordination, the eyelids wiU close, and there wiU be muscle weakness and lack of energy due to the lack of oxygen. About 6 mg of the cobra neurotoxin is sufficient to cause death, which occurs very rapidly, for example a woman in Sri Lanka died fifteen minutes after being bitten by a cobra. 

Cobra neurotoxin Indian or Formosan cobra venom... 

Abstract - The crucial details for the interpretation of spatial structures and intermolecular interactions of peptides and proteins could be revealed by proper combination of physical and chemical techniques. The paper presents the results of the combined approach for the evaluation of the conformation in solution of honey-bee venom component apamin (18 membered polypeptide), of three dimensional structure of Central Asian cobra neurotoxin II (61 amino acid residues), and of the topography of its binding site with acetylcholine receptor Torpedo Marmorata. 

DNP signal enhancement also facilitated the structural investigation of the Asian cobra neurotoxin II bound to the ligand-gated ion channel lucotiific acetylcholine receptor (nAChR) obtained from the electric organ of an electric ray [230, 231]. Despite the low concentration of the N- and 1,3- C- or 2- C-glycerol-labeled toxin, a decent 2D correlation spectrum could be recorded within 14 h. 

The similarity of the primary structure of different sea snake venoms has already been discussed. Postsynaptic neurotoxins from Elapidae venom have been extensively studied. Elapidae include well-known snakes such as cobra, krait, mambas, coral snakes, and all Australian snakes. Like sea snake toxins, Elapidae toxins can also be grouped into short-chain (Type I) and long-chain (Type II) toxins. Moreover, two types of neurotoxins are also similar to cardiotoxins, especially in the positions of disulfide bonds. However, amino acid sequences between cardiotoxins and sea snake and Elapidae neurotoxins are quite different. In comparing the sequence of sea snake and Elapidae neurotoxins, there is a considerable conservation in amino acid sequence, but the difference is greater than among the various sea snake toxins. 

Neurotoxin obtained from the Formosan cobra (Naja naja atra). It is a relatively heat stable, water soluble, crystalline solid. 

Elapidae Cobras Kraits Coral snakes Neurotoxin (some very potent) Fixed fangs, usually low dose Nervous system effects, paralysis, numbness, respiratory failure... 

Long neurotoxin from the venom of the Asian cobra... 

With cobra venom, the major effect is due to a toxin that acts on the nervous system. This neurotoxin is a small molecule, which can distribute throughout the body rapidly It acts like curare, paralysing the centre in the brain that controls breathing. By acting at the point where nerves control muscles it blocks the transmission of nerve impulses and causes muscle weakness and again affects breathing. The eyelids droop and speech becomes incoordinated. 

Not only the Kraits produce a-neurotoxins. The Indian Cobra Cobra naja naja) also utilises one of fhe mosf pofenf of all fhe snake toxins, cobratoxin, which is also an a-neurotoxin. Cobratoxin is phenomenally toxic only 4.5 mg is needed to kill a human. In fact, a single Cobra can produce sufficient toxin to kill ten men. The Sea Kraits (e.g. Laticauda semifasciata from Malaysia) are the most toxic of all snakes they produce erabutoxin which is an a-neurotoxin of unbelievable potency, but fortunately, as discussed earlier, they have small jaws, which makes it difficult for them to bite a human. 

For many who study the chemistry of venoms, the neurotoxins hold particular interest. One example would be the polypeptide toxin cobrotoxin that was isolated from the Formosan cobra and analyzed in 1965 by Chen-Chung Yang, a distingmshed chair professor at Tsing Hua University in Taiwan. The primary structure of this neurotoxin is indicated in Figure 1, along with some components of its secondary structure. There are sixty-two residues in the primary structure and four di-sulfide bonds in the secondary structure. If even one of these di-sulfide bonds is somehow disrupted, the polypeptide is rendered nontoxic. This points to the fact that secondary structure is important even in small polypeptides, not only full-size proteins. 

Important toxins are cobramine A and B from cobra toxin and crotactine and crotamine from crotox-in, the toxin of the North American rattlesnake. The toxic proteins are classified according to their mode of action cardiotoxins, neuFotoxins and protease inhibitors (with inhibitory activity toward chymotrypsin and trypsin). Cardiotoxins (heart muscle poisons) cause an irreversible depolarization of the cell membranes of heart muscle and nerve cells. Neurotoxins (nerve poisons) show curare-like activity they prevent neuromuscular transmission by blocking the receptors for the transmitters at the synapses of autonomic nerve endings and at the motor end plate of skeletal muscle. Protease inhibitors inhibit acetylcholine esterase and similar enzymes involved in nerve transmission. 

CONTEXT The secondary structure of a protein is crucial to its biological activity, whether for good or ill. Snake venoms consist of saliva with a high proportion of toxic proteins. Cobra venom in particular acts on the victim by means of neurotoxins, proteins that attack the nervous system, in this case by blocking the acetylcholine receptors on the membranes of muscle cells. Normally, when acetylcholine... 

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