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XB-ART-15622
Neuroreport 1997 Nov 10;816:3591-6. doi: 10.1097/00001756-199711100-00034.
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Paradoxical allosteric effects of competitive inhibitors on neuronal alpha7 nicotinic receptor mutants.

Bertrand S , Devillers-Thiéry A , Palma E , Buisson B , Edelstein SJ , Corringer PJ , Changeux JP , Bertrand D .


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Mutation of the conserved leucine residue, in the second transmembrane domain of the neuronal alpha7 acetylcholine receptor to a threonine (L247T) causes pleiotropic alterations of receptor properties. In this study we examined the effects of competitive inhibitors on the alpha7-L247T physiological responses. While the alpha7 competitive inhibitor dihydro-beta-erythroidine evoked a current comparable to that induced by ACh, other inhibitors such as methyllycaconitine (MLA) and alpha-bungarotoxin (alpha-Bgt) caused a blockade of alpha7-L247T to ACh activation. When applied in the absence of ACh, MLA or alpha-Bgt reduced the cell leakage current, showing that alpha7-L247T displays a significant fraction (10%) of spontaneously open channels. These data can be interpreted in terms of an allosteric model, assuming that the L247T mutant possesses a low isomerization constant L and that MLA and alpha-Bgt stabilize the closed, resting state.

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