Novel pore-lining residues in CFTR that govern permeation and open-channel block.
The cystic fibrosis transmembrane conductance regulator (CFTR) is both a member of the ATP-binding cassette superfamily and a Cl(-)-selective ion channel. We investigated the permeation pathway of human CFTR with measurements on conduction and open-channel blockade by diphenylamine-2-carboxylic acid (DPC). We used site-directed mutagenesis and oocyte expression to locate residues in transmembrane domain (TM) 6 and TM 12 that contact DPC and control rectification and single-channel conductances. Thus, TM 12 and the previously investigated TM 6 line the CFTR pore. In each TM, residues in contact with DPC are separated by two turns of an alpha helix. The contributions of TM 6 and TM 12 to DPC block and Cl- permeation, however, are not equivalent. The resulting structural model for the conduction pathway may guide future studies of permeation in other Cl- channels and ATP-binding cassette transporters.
McDonough
S
S
Division of Biology, California Institute of Technology, Pasadena 91125.
Davidson
N
N
Lester
H A
HA
McCarty
N A
NA
D000595:Amino Acid Sequence; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D003550:Cystic Fibrosis / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D004553:Electric Conductivity; D005110:Extracellular Space / Q000378:metabolism; D007473:Ion Channels / Q000037:antagonists & inhibitors*; D008565:Membrane Proteins / Q000235:genetics* / Q000502:physiology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010539:Permeability; D051381:Rats; D062367:ortho-Aminobenzoates / Q000378:metabolism / Q000494:pharmacology
D002121:Calcium Channel Blockers; D007473:Ion Channels; D008565:Membrane Proteins; D062367:ortho-Aminobenzoates; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; C001209:fenamic acid