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Polyamine spider toxins and NMDA receptors: structural basis for channel block and binding of argiotoxin636

MPS-Authors
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Raditsch,  Martin
Department of Cell Physiology, Max Planck Institute for Medical Research, Max Planck Society;

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Geyer,  Matthias
Emeritus Group Biophysics, Max Planck Institute for Medical Research, Max Planck Society;

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Kalbitzer,  Hans Robert
Emeritus Group Biophysics, Max Planck Institute for Medical Research, Max Planck Society;

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Ruppersberg,  J. Peter
Department of Cell Physiology, Max Planck Institute for Medical Research, Max Planck Society;

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Jahn,  Werner
Emeritus Group Biophysics, Max Planck Institute for Medical Research, Max Planck Society;

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Witzemann,  Veit
Department of Molecular Neurobiology, Max Planck Institute for Medical Research, Max Planck Society;
Department of Cell Physiology, Max Planck Institute for Medical Research, Max Planck Society;

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Citation

Raditsch, M., Geyer, M., Kalbitzer, H. R., Ruppersberg, J. P., Jahn, W., & Witzemann, V. (1996). Polyamine spider toxins and NMDA receptors: structural basis for channel block and binding of argiotoxin636. European Journal of Biochemistry, 240, 416-426. Retrieved from http://www.ejbiochem.org/cgi/content/abstract/240/2/416?maxtoshow%3D%26HITS%3D10%26hits%3D10%26RESULTFORMAT%3D%26searchid%3D1021620596745_21%26stored_search%3D%26FIRSTINDEX%3D0%26volume%3D240%26firstpage%3D416%26fdate%3D1%2F1%2F1996%26tdate%3D12%2F31%2F1996%26journalcode%3Dejbiochem%3A.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0024-3DA2-0
Abstract
Recombinant N-methyl-D-aspartate receptors composed of NR1/NR2A subunits were expressed in Xenopus oocytes to analyse the voltage- dependent and use-dependent channel blocking activity of argiotoxin636. Functional assays demonstrate that the toxin competes with other open channel blockers such as Mg2+ and MK-801. Direct binding or competition assays using radiolabeled ligands and isolated rat brain membranes, in contrast, reveal no specific binding or yield binding constants which differ by orders of magnitude from the IC50 values of the functional assays. One explanation is that argiotoxin636 does not bind with high affinity to the inhibitory site in the N-methyl-D-aspartate-receptor channel under in vitro conditions when membranes are depolarised. The structure of argiotoxin636 was investigated by NMR spectroscopy. In solution the positively charged argiotoxin636 acquires an extended conformation and its dimensions might allow permeation deep into the channel. In the absence of direct structural information on the channel protein, the detailed analysis of blockade in conjunction with structural information, as provided here, may be of aid in the deduction of structural features of glutamate-receptor channel ion pores