Rowan, E G (2001) What does beta-bungarotoxin do at the neuromuscular junction? Toxicon, 39 (1). pp. 107-118. ISSN 0041-0101Full text not available in this repository. (Request a copy from the Strathclyde author)
beta-Bungarotoxin from the Taiwan banded krait, Bungarus multicinctus is a basic protein (pI=9.5), with a molecular weight of 21,800 consisting of two different polypeptide subunits. A phospholipase A(2) subunit named the A-chain and a non-phospholipase A(2) subunit named the B-chain, which is homologous to Kunitz protease inhibitors. The A-chain and the B-chain are covalently linked by one disulphide bridge. On mouse hemi-diaphragm nerve-muscle preparations, partially paralysed by lowering the external Ca(2+) concentration, beta-bungarotoxin classically produces triphasic changes in the contraction responses to indirect nerve stimulation. The initial transient inhibition of twitches (phase 1) is followed by a prolonged facilitatory phase (phase 2) and finally a blocking phase (phase 3). These changes in twitch tension are mimicked, to some extent, by similar changes to end plate potential amplitude and miniature end plate potential frequency. The first and second phases are phospholipase-independent and are thought to be due to the B-chain (a dendrotoxin mimetic) binding to or near to voltage-dependent potassium channels. The last phase (phase 3) is phospholipase dependent and is probably due to phospholipase A(2)-mediated destruction of membrane phospholipids in motor nerve terminals.
|Keywords:||motor nerve terminals, bungaris-multicinctus venom, taiwan banded krait, amino-acid substitutions, phospholipase-a activity, p-bromophenacyl bromide, K+ channel, acetylcholine-release, potassium current, binding-sites, Therapeutics. Pharmacology, Toxicology|
|Subjects:||Medicine > Therapeutics. Pharmacology|
|Department:||Faculty of Science > Strathclyde Institute of Pharmacy and Biomedical Sciences|
|Depositing user:||Dr EG Rowan|
|Date Deposited:||18 Nov 2010 15:47|
|Last modified:||04 May 2016 14:19|