β-Bungarotoxin | |
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Identifiers | |
Organism | |
Symbol | N/A |
CAS number |
12778-32-4 β1:65862-89-7 β2:82446-04-6 |
β-Bungarotoxin is a form of bungarotoxin that is fairly common in Krait (Bungarus multicinctus) venoms. It is the prototypic class of snake β- neurotoxins. There are at least five isoforms, coded β1 to β5, assembled from different combinations of A and Bchains. [1]
The toxin is a heterodimer of two chains. The A chain confers phospholipase A2 (PLP A2) activity, and the B chain, like dendrotoxins, have a Kunitz domain. There are many isoforms of these chains: examples of A chains include A1 ( P00617), A3 ( P00619), and A4 ( P17934), and examples of B chains include B2 ( P00989) and B3 ( Q75S50). The B chain plays a functional role in inducing apoptosis. [2]
The target of this neurotoxin is at the presynaptic terminal, where it blocks release of acetylcholine. It seems to do so by blocking the phosphorylation of MARCKS. [3] 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. [4]
Neurobiological research from the late 1980s has found that beta-bungarotoxin selectively binds to (125)I-DTX-I receptor.