DISULFONIC STILBENE BLOCK OF CYSTIC-FIBROSIS TRANSMEMBRANE CONDUCTANCE REGULATOR CL- CHANNELS EXPRESSED IN A MAMMALIAN-CELL LINE AND ITS REGULATION BY A CRITICAL PORE RESIDUE

1. The disulphonic stilbenes 4,4'-dinitrostilbene-2,2'-disulphonic aci d (DNDS) and 4,4'-diisothiocyanostilbene 2,2'-disulphonic acid (DIDS) were shown to cause a voltage-dependent inhibition of macroscopic cyst ic fibrosis transmembrane conductance regulator (CFTR) Cl- currents ex pressed in baby hamster kidney cells when applied to the cytoplasmic f ace of the membrane. These compounds are known to be relatively ineffe ctive at blocking CFTR from the extracellular side of the membrane. 2. Mutation of a positively charged arginine, previously suggested to be located in the channel pore (R347), to a negatively charged aspartate significantly reduced the affinity of block by both DNDS and DIDS, su ggesting that this residue contributes to the binding site for disulph onic stilbenes. 3. It is suggested that the CFTR Cl- channel may conta in a relatively large inner vestibule in which a number of large anion s bind and block Cl- permeation. Arginine 347 may be involved in anion binding within this region.