β-Bungarotoxin is a form of bungarotoxin that is fairly common in

Krait ''Bungarus'' (commonly known as kraits ) is a genus of venomous snakes in the Family (biology), family Elapidae. The genus is native to Asia. Often found on the floor of tropical forests in South Asia, Southeast Asia and Southern China, they are ...

(''Bungarus multicinctus'')

venom Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...

s. It is the prototypic class of snake β-

neurotoxin Neurotoxins are toxins that are destructive to nervous tissue, nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insult (medical), insultsSpencer 2000 that can adversely affect function ...

s. There are at least five isoforms, coded β₁ to β₅, assembled from different combinations of A and Bchains. The toxin is a heterodimer of two chains. The A chain confers

phospholipase A2 The enzyme phospholipase A2 (EC 3.1.1.4, PLA2, systematic name phosphatidylcholine 2-acylhydrolase) catalyses the cleavage of fatty acids in position 2 of phospholipids, hydrolyzing the bond between the second fatty acid "tail" and the glycero ...

(PLP A2) activity, and the B chain, like

dendrotoxin Dendrotoxins are a class of presynaptic neurotoxins produced by mamba snakes ('' Dendroaspis'') that block particular subtypes of voltage-gated potassium channels in neurons, thereby enhancing the release of acetylcholine at neuromuscular junctio ...

s, have a

Kunitz domain Kunitz domains are the active protein domain, domains of proteins that inhibit the function of protease, protein degrading enzymes or, more specifically, domains of Kunitz-type are Protease inhibitor (biology), protease inhibitors. They are relat ...

. There are many isoforms of these chains: examples of A chains include A1 (), A3 (), and A4 (), and examples of B chains include B2 () and B3 (). The B chain plays a functional role in inducing apoptosis. The target of this neurotoxin is at the

presynaptic terminal Chemical synapses are biological junctions through which neurons' signals can be sent to each other and to non-neuronal cells such as those in muscles or glands. Chemical synapses allow neurons to form circuits within the central nervous syste ...

, where it blocks release of

acetylcholine Acetylcholine (ACh) is an organic compound that functions in the brain and body of many types of animals (including humans) as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Par ...

. It seems to do so by blocking the phosphorylation of

MARCKS Marcks is a surname. Notable people with the surname include: * Erich Marcks (1891–1944), German general * Gerhard Marcks (1889–1981), German sculptor * Greg Marcks (born 1976), American director, writer and actor * Megan Marcks (born 1972), ...

. It is thought that the dendrotoxin-like B chain acts first by inhibition of ion channels, causing cessation of twitches followed by a prolonged facilitatory phase. The A chain (bearing phospholipase activity) then induces a blocking phase by destruction of phospholipids.

Binding sites

Neurobiological research from the late 1980s has found that beta-bungarotoxin selectively binds to (125)I-DTX-I receptor.

References

Ion channel toxins Snake toxins Bungarus Acetylcholine release inhibitors {{nervous-system-drug-stub

Binding sites

See also

References