RT Journal Article SR Electronic T1 Preferential Interaction of ω-Conotoxins with Inactivated N-type Ca2+ Channels JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 3002 OP 3013 DO 10.1523/JNEUROSCI.17-09-03002.1997 VO 17 IS 9 A1 Jonathan W. Stocker A1 Laszlo Nadasdi A1 Richard W. Aldrich A1 Richard W. Tsien YR 1997 UL http://www.jneurosci.org/content/17/9/3002.abstract AB The selective block of N-type Ca2+ channels by ω-conotoxins has been a hallmark of these channels, critical in delineating their biological roles and molecular characteristics. Here we report that the ω-conotoxin-channel interaction depends strongly on channel gating. N-type channels (α1B, α2, and β1) expressed in Xenopusoocytes were blocked with a variety of ω-conotoxins, including ω-CTx-GVIA, ω-CTx-MVIIA, and SNX-331, a derivative of ω-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 ω-conotoxin block completely reversible. These effects could be accounted for by a modulated receptor model, in which toxin dissociation from the inactivated state is ∼60-fold slower than from the resting state. Because ω-conotoxins act exclusively outside cells, our results suggest that voltage-dependent inactivation of Ca2+channels must be associated with an externally detectable conformational change.