title: Location of a permeant anion binding site in the cystic fibrosis transmembrane conductance regulator chloride channel pore.
abstract: In the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel, lyotropic anions with high permeability also bind relatively tightly within the pore. However, the location of permeant anion binding sites, as well as their relationship to anion permeability, is not known. We have identified lysine residue K95 as a key determinant of permeant anion binding in the CFTR pore. Lyotropic anion binding affinity is related to the number of positively charged amino acids located in the inner vestibule of the pore. However, mutations that change the number of positive charges in this pore region have minimal effects on anion permeability. In contrast, a mutation at the narrow pore region alters permeability with minimal effects on anion binding. Our results suggest that a localized permeant anion binding site exists in the pore; however, anion binding to this site has little influence over anion permeability. Implications of this work for the mechanisms of anion recognition and permeability in CFTR are discussed.
authors: Department of Physiology and Biophysics, Dalhousie University, PO Box 15000, Halifax, NS, B3H 4R2, Canada.
authors: Hussein N
authors: HN
authors: Rubaiy
authors: Paul
authors: P
authors: Linsdell
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D000838:Anions / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D002478:Cells, Cultured; D006224:Cricetinae; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008239:Lysine / Q000737:chemistry; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010539:Permeability; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D000838:Anions; C505032:CFTR protein, human; D050505:Mutant Proteins; D011994:Recombinant Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D008239:Lysine