Referenced in: none

Automatically associated channels: Kir2.3

Title: Carbodiimide modification reduces the conductance and increases the tetrodotoxin sensitivity in batrachotoxin-modified sodium channels.

Authors: L D Chabala, O S Andersen

Journal, date & volume: Pflugers Arch., 1992 Jun , 421, 262-9

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/1326748

Abstract
The relationship between the channel entrance and the tetrodotoxin (TTX) binding site was investigated by chemical modification at the extracellular surface of bilayer-incorporated batrachotoxin-(BTX) modified sodium channels using an impermeant carbodiimide in the presence or absence of exogenous nucleophiles. Two (classes of) groups could be modified such that the open-channel conductance was decreased while TTX binding was unaffected, and TTX did not protect against this modification. Because the final conductance level depends on the exogenous nucleophile, each covalent modification appears to involve a carboxyl group. In addition, a third (carboxyl) group could be modified such that TTX binding affinity was increased. These results suggest that the channel entrance and the TTX binding site are spatially separate, which supports previous suggestions that the mechanism by which guanidinium toxins close sodium channels involves a conformational change subsequent to toxin binding.