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Kinetic evidence for different mechanisms of interaction of black mamba toxins MT alpha and MT beta with muscarinic receptors
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2001 (English)In: Toxicon, ISSN 0041-0101, E-ISSN 1879-3150, Vol. 39, no 2-3, 377-382 p.Article in journal (Refereed) Published
Abstract [en]

By studying the influence of two toxins from the black mamba Dendroaspis polylepis on the kinetics of [H-3]-N-methylscopolamine binding to muscarinic acetylcholine receptors from rat cerebral cortex, it was revealed that these toxins, MT alpha and MT beta, interact with the receptors via kinetically distinct mechanisms. MT beta bound to receptors in a one-step, readily reversible process with the dissociation constant K-d = 5.3 mu M. The binding mechanism of MT alpha was more complex, involving at least two consecutive steps. A fast receptor-toxin complex formation (K-T = 3.8 mu M) was followed by a slow process of isomerisation of this complex (k(i) = 1.8 x 10(-2) s(-1), half-time 39 s). A similar two-step interaction mechanism has been established for a related toxin, MT2 from the green mamba D. angusticeps (K-T = 1.4 mu M, k(i) = 8.3 x 10(-4) s(-1), half-time 840 s). The slow isomerisation process delays the effect of MT alpha and MT2, but increases their apparent potency compared to toxins unable to induce the isomerisation process.

Place, publisher, year, edition, pages
2001. Vol. 39, no 2-3, 377-382 p.
Keyword [en]
snake toxins (Dendroaspis polylepis), muscarinic acetylcholine, receptor, muscarinic toxin, binding mechanism, amino-acid-sequence, acetylcholine-receptors, binding, antagonist
URN: urn:nbn:se:kth:diva-20049ISI: 000089441800026OAI: diva2:338742
QC 20100525Available from: 2010-08-10 Created: 2010-08-10Bibliographically approved

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Jolkkonen, Mikael
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