View source for Biology:Beta-bungarotoxin

{{DISPLAYTITLE:''beta''-bungarotoxin}}
{{Infobox nonhuman protein
| Name = ''β''<sub>2</sub>-Bungarotoxin
| image = PDB 1bun EBI.jpg
| width = 200px
| caption = Schematic diagram of the three-dimensional [[Biology:Protein structure|structure]] of β-bungarotoxin ({{PDB|1bun}}).
| Organism = Bungarus multicinctus
| TaxID = 
| Symbol = N/A
| CAS_number = 12778-32-4
| CAS_supplemental = β<sub>1</sub>:65862-89-7<br />β<sub>2</sub>:82446-04-6
| DrugBank = 
}}

'''β-Bungarotoxin''' is a form of [[Biology:Bungarotoxin|bungarotoxin]] that is fairly common in Krait (''Bungarus multicinctus'') [[Chemistry:Snake venom|venom]]s. It is the prototypic class of snake '''β-neurotoxins'''. There are at least five isoforms, coded β<sub>1</sub> to β<sub>5</sub>, assembled from different combinations of A and Bchains.<ref>{{cite journal |last1=Kondo |first1=K |last2=Toda |first2=H |last3=Narita |first3=K |last4=Lee |first4=CY |title=Amino acid sequences of three beta-bungarotoxins (beta 3-, beta 4-, and beta 5- bungarotoxins) from Bungarus multicinctus venom. Amino acid substitutions in the A chains. |journal=Journal of Biochemistry |date=May 1982 |volume=91 |issue=5 |pages=1531–48 |doi=10.1093/oxfordjournals.jbchem.a133844 |pmid=7096305}}</ref>

The toxin is a heterodimer of two chains. The A chain confers [[Biology:Phospholipase A2|phospholipase A2]] (PLP A2) activity, and the B chain, like [[Biology:Dendrotoxin|dendrotoxin]]s, have a [[Biology:Kunitz domain|Kunitz domain]]. There are many isoforms of these chains: examples of A chains include A1 ({{UniProt|P00617}}), A3 ({{UniProt|P00619}}), and A4 ({{UniProt|P17934}}), and examples of B chains include B2 ({{UniProt|P00989}}) and B3 ({{UniProt|Q75S50}}). The B chain plays a functional role in inducing apoptosis.<ref name="pmid18037462">{{cite journal |vauthors=Cheng YC, Wang JJ, Chang LS |title=B chain is a functional subunit of beta-bungarotoxin for inducing apoptotic death of human neuroblastoma SK-N-SH cells |journal=Toxicon |volume=51 |issue=2 |pages=304–15 |date=February 2008 |pmid=18037462 |doi=10.1016/j.toxicon.2007.10.006}}</ref>

The target of this neurotoxin is at the presynaptic terminal, where it blocks release of [[Chemistry:Acetylcholine|acetylcholine]]. It seems to do so by blocking the phosphorylation of MARCKS.<ref>{{cite journal |last1=Ueno |first1=E |last2=Rosenberg |first2=P |title=Mechanism of action of beta-bungarotoxin, a presynaptically acting phospholipase A2 neurotoxin: its effect on protein phosphorylation in rat brain synaptosomes. |journal=Toxicon |date=1996 |volume=34 |issue=11–12 |pages=1219–27 |pmid=9027977|doi=10.1016/S0041-0101(96)00113-4 }}</ref> 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.<ref>{{cite journal |last1=Rowan |first1=EG |title=What does beta-bungarotoxin do at the neuromuscular junction? |journal=Toxicon |date=January 2001 |volume=39 |issue=1 |pages=107–18 |pmid=10936627|doi=10.1016/S0041-0101(00)00159-8 }}</ref>

==Binding Sites==

Neurobiological research from the late 1908s has found that beta-bungarotoxin selectively binds to (125)I-DTX-I receptor.

==See also==
*[[Biology:Alpha-Bungarotoxin|alpha-Bungarotoxin]]

== References ==
{{Reflist}}

{{Toxins}}
{{Acetylcholine metabolism and transport modulators}}

{{DEFAULTSORT:Bungarotoxin, beta-}}
[[Category:Ion channel toxins]]
[[Category:Vertebrate toxins]]
[[Category:Bungarus]]



{{Sourceattribution|Beta-bungarotoxin|1}}