α-Cobratoxin is a substance of the venom of certain Naja

Naja

Naja is a genus of venomous elapid snakes. Although there are several other genera that share the common name, Naja are the most recognized and most widespread group of snakes commonly known as cobras. The genus Naja consists of 20 to 22 species, but has undergone several taxonomic revisions in...

cobras. It is a muscle-type nicotinic acetylcholine receptor (nAChR) antagonist, which causes paralysis by preventing the binding of acetylcholine

Acetylcholine

The chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans...

 to the nAChR.

Source

α-Cobratoxin is a neurotoxin from the venom of certain Naja cobras, such as Naja atra

Naja atra

The Chinese cobra The Chinese cobra The Chinese cobra (Naja atra, also known as Taiwanese cobra, is a species of genus Naja found mostly in southern China and Taiwan. Theodore Edward Cantor first described the iridescent black monocled cobra from Chusan Island in 1842...

and Naja siamensis

Naja siamensis

Naja siamensis or the Indo-Chinese Cobra is a species of spitting cobra found in Southeast Asia. It is one of the six spitting cobras found in Asia.-Description:...

(the monocled cobra)

Chemistry

α-Cobratoxin consists of 71 amino acid residues and 5 disulfide bridges . It is also known as long neurotoxin 1, neurotoxin 3, or CbTx. It belongs to the type II alpha-neurotoxin subfamily, which also includes alpha-bungarotoxin.

Target

Cobratoxin binds with high affinity to ligand gated nicotinic acetylcholine receptor (nAChR) , which play an important role in synaptic transmission both in the central nervous system and at the neuromuscular junction

Neuromuscular junction

A neuromuscular junction is the synapse or junction of the axon terminal of a motor neuron with the motor end plate, the highly-excitable region of muscle fiber plasma membrane responsible for initiation of action potentials across the muscle's surface, ultimately causing the muscle to contract...

 (NMJ) . It has an affinity for the chick neuronal α7 nAChR of 6 nM and for the nAchR from the Torpedo NMJ of 39 pM .

Mode of action

Cobratoxin binds to the ligand-binding pocket between the α/γ or α/δ nAChR subunits . It causes a postsynaptic block at the NMJ nAChRs by preventing the binding of acetylcholine to its receptor. Long neurotoxins like Cobratoxin also block neuronal α7 nAChRs , but it is unclear how effectively the long neurotoxin

Neurotoxin

A neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels. Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...

 can reach the central nervous system

Central nervous system

The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...

 (CNS).

Treatment

Researchers are trying to develop a vaccine against the toxin by using a replicant-deficient adenovirus containing mutated cobratoxin .