Referenced in: none

Automatically associated channels: Kv10.1

Title: CFTR: Ligand exchange between a permeant anion ([Au(CN)2]-) and an engineered cysteine (T338C) blocks the pore.

Authors: José R Serrano, Xuehong Liu, Erik R Borg, Christopher S Alexander, C Frank Shaw, David C Dawson

Journal, date & volume: Biophys. J., 2006 Sep 1 , 91, 1737-48

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/16766608

Abstract
Previous attempts to identify residues that line the pore of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel have utilized cysteine-substituted channels in conjunction with impermeant, thiol-reactive reagents like MTSET+ and MTSES-. We report here that the permeant, pseudohalide anion [Au(CN)2]- can also react with a cysteine engineered into the pore of the CFTR channel. Exposure of Xenopus oocytes expressing the T338C CFTR channel to as little as 100 nM [Au(CN)2]- produced a profound reduction in conductance that was not reversed by washing but was reversed by exposing the oocytes to a competing thiol like DTT (dithiothreitol) and 2-ME (2-mercaptoethanol). In detached, inside out patches single-channel currents were abolished by [Au(CN)2]- and activity was not restored by washing [Au(CN)2]- from the bath. Both single-channel and macroscopic currents were restored, however, by exposing [Au(CN)2]- -blocked channels to excess [CN]-. The results are consistent with the hypothesis that [Au(CN)2]- can participate in a ligand exchange reaction with the cysteine thiolate at 338 such that the mixed-ligand complex, with a charge of -1, blocks the anion conduction pathway.