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A small basic protein (Mr57000). It contains 62 amino acids in a single chain, cross-linked by four disulfide bonds. The toxin comprises 10% of the venom by weight. It is a neurotoxin that is secreted by glands of the cobra snake and injected into its prey via immobile, grooved fangs. Cobratoxin may be radiolabeled and used as a specific radioligand in binding studies performed on acetylcholine receptors. Cobratoxin is absorbed from the subcutaneous tissues and is distributed throughout the body. After intoxication, high concentrations are found at the motor endplates of neuromuscular junctions, where it irreversibly binds to acetylcholine receptors. The primary action is similar to that of curare, but the binding process is slower.