title: Demonstration that CFTR is a chloride channel by alteration of its anion selectivity.
abstract: Expression of the cystic fibrosis transmembrane conductance regulator (CFTR) generates adenosine 3',5'-monophosphate (cAMP)-regulated chloride channels, indicating that CFTR is either a chloride channel or a chloride channel regulator. To distinguish between these possibilities, basic amino acids in the putative transmembrane domains were mutated. The sequence of anion selectivity of cAMP-regulated channels in cells containing either endogenous or recombinant CFTR was bromide greater than chloride greater than iodide greater than fluoride. Mutation of the lysines at positions 95 or 335 to acidic amino acids converted the selectivity sequence to iodide greater than bromide greater than chloride greater than fluoride. These data indicate that CFTR is a cAMP-regulated chloride channel and that lysines 95 and 335 determine anion selectivity.
authors.affiliation: Howard Hughes Medical Institute, Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242.
authors.forename: M P
authors.initials: MP
authors.lastname: Anderson
authors.forename: R J
authors.initials: RJ
authors.lastname: Gregory
authors.forename: S
authors.initials: S
authors.lastname: Thompson
authors.forename: D W
authors.initials: DW
authors.lastname: Souza
authors.forename: S
authors.initials: S
authors.lastname: Paul
authors.forename: R C
authors.initials: RC
authors.lastname: Mulligan
authors.forename: A E
authors.initials: AE
authors.lastname: Smith
authors.forename: M J
authors.initials: MJ
authors.lastname: Welsh
mesh_terms: D000595:Amino Acid Sequence; D018118:Chloride Channels; D002712:Chlorides / Q000502:physiology*; D000242:Cyclic AMP / Q000502:physiology; D003550:Cystic Fibrosis / Q000503:physiopathology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D004252:DNA Mutational Analysis; D004553:Electric Conductivity; D006367:HeLa Cells; D006801:Humans; D066298:In Vitro Techniques; D007473:Ion Channels / Q000235:genetics / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000502:physiology; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D014162:Transfection
chemical_list: C505032:CFTR protein, human; D018118:Chloride Channels; D002712:Chlorides; D007473:Ion Channels; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000242:Cyclic AMP