title: CFTR is a monomer: biochemical and functional evidence.
abstract: Although the CFTR protein alone is sufficient to generate a regulated chloride channel, it is unknown how many of the polypeptides form the channel. Using biochemical and functional assays, we demonstrate that the CFTR polypeptide is a monomer. CFTR sediments as a monomer in a linear, continuous sucrose gradient. Cells co-expressing different epitope-tagged CFTR provide no evidence of co-assembly in immunoprecipitation and nickel affinity binding experiments. Co-expressed wild-type and DF508 CFTR are without influence on each other in their ability to progress through the secretory pathway, suggesting they do not associate in the endoplasmic reticulum. No hybrid conducting single channels are seen in planar lipid bilayers with which membrane vesicles from cells co-expressing similar amounts of two different CFTR conduction species have been fused.
authors.affiliation: Mayo Foundation and Mayo Clinic Scottsdale, S. C. Johnson Medical Research Center, 13400 E. Shea Blvd., Scottsdale, AZ 85259, USA.
authors.forename: J-H
authors.initials: JH
authors.lastname: Chen
authors.forename: X-B
authors.initials: XB
authors.lastname: Chang
authors.forename: A A
authors.initials: AA
authors.lastname: Aleksandrov
authors.forename: J R
authors.initials: JR
authors.lastname: Riordan
mesh_terms: D000818:Animals; D018118:Chloride Channels / Q000737:chemistry*; D006224:Cricetinae; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification; D000939:Epitopes; D015870:Gene Expression; D006801:Humans; D007668:Kidney / Q000502:physiology; D008051:Lipid Bilayers / Q000737:chemistry*; D008564:Membrane Potentials / Q000502:physiology; D008861:Microsomes / Q000737:chemistry / Q000502:physiology; D020836:Protein Structure, Quaternary; D011994:Recombinant Proteins; D013045:Species Specificity
chemical_list: C505032:CFTR protein, human; D018118:Chloride Channels; D000939:Epitopes; D008051:Lipid Bilayers; D011994:Recombinant Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator