title: Direct comparison of the functional roles played by different transmembrane regions in the cystic fibrosis transmembrane conductance regulator chloride channel pore.
abstract: The cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel contains 12 transmembrane (TM) regions that are presumed to form the channel pore. However, little is known about the relative functional contribution of different TM regions to the pore. We have used patch clamp recording to investigate the functional consequences of point mutations throughout the six transmembrane regions in the N-terminal part of the CFTR protein (TM1-TM6). A range of specific functional assays compared the single channel conductance, anion binding, and anion selectivity properties of different channel variants. Overall, our results suggest that TM1 and -6 play dominant roles in forming the channel pore and determining its functional properties, with TM5 perhaps playing a lesser role. In contrast, TM2, -3, and -4 appear to play only minor supporting roles. These results define transmembrane regions 1 and 6 as major contributors to the CFTR channel pore and have strong implications for emerging structural models of CFTR and related ATP-binding cassette proteins.
authors.affiliation: Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia B3H 1X5, Canada.
authors.forename: Ning
authors.initials: N
authors.lastname: Ge
authors.forename: Chantal N
authors.initials: CN
authors.lastname: Muise
authors.forename: Xiandi
authors.initials: X
authors.lastname: Gong
authors.forename: Paul
authors.initials: P
authors.lastname: Linsdell
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D000818:Animals; D000838:Anions; D002460:Cell Line; D006224:Cricetinae; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000737:chemistry / Q000235:genetics*; D004594:Electrophysiology; D008954:Models, Biological; D016296:Mutagenesis; D009154:Mutation; D018408:Patch-Clamp Techniques; D010641:Phenotype; D017354:Point Mutation; D017434:Protein Structure, Tertiary; D013861:Thiocyanates / Q000494:pharmacology
chemical_list: D000838:Anions; D013861:Thiocyanates; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000255:Adenosine Triphosphate; C031760:thiocyanate