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XB-ART-16594
J Neurosci 1997 May 01;179:3002-13.
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Preferential interaction of omega-conotoxins with inactivated N-type Ca2+ channels.

Stocker JW , Nadasdi L , Aldrich RW , Tsien RW .


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The selective block of N-type Ca2+ channels by omega-conotoxins has been a hallmark of these channels, critical in delineating their biological roles and molecular characteristics. Here we report that the omega-conotoxin-channel interaction depends strongly on channel gating. N-type channels (alpha1B, alpha2, and beta1) expressed in Xenopus oocytes were blocked with a variety of omega-conotoxins, including omega-CTx-GVIA, omega-CTx-MVIIA, and SNX-331, a derivative of omega-CTx-MVIIC. Changes in holding potential (HP) markedly altered the severity of toxin block and the kinetics of its onset and removal. Notably, strong hyperpolarization renders omega-conotoxin block completely reversible. These effects could be accounted for by a modulated receptor model, in which toxin dissociation from the inactivated state is approximately 60-fold slower than from the resting state. Because omega-conotoxins act exclusively outside cells, our results suggest that voltage-dependent inactivation of Ca2+ channels must be associated with an externally detectable conformational change.

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Species referenced: Xenopus laevis
Genes referenced: anxa7 vsig1

References [+] :
Aiyar, Topology of the pore-region of a K+ channel revealed by the NMR-derived structures of scorpion toxins. 1995, Pubmed