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Preparation of Isolated Surface

Membranes from Cystic Fibrosis Airway Epithelial cells· Alan D. Harsch, M.D.;t lin Xu, M.D.;t Charles L. Bevins, M.D.;t Mary Catherine Glick, Ph.D.;§ and Thomas F. Scanlin, M. D. til

fibrosis is the most common deadly inherited C ystic disease in the white population, and the classic clinical

triad of chronic lung disease, pancreatic insufficiency, and elevated sweat electrolytes has been well described. 1 The CF gene has been identified,2 and the most common mutation is the deletion of 3 base pairs coding for phenylalanine at position 508 (4F508)' Approximately 70% of CF patients are either heterozygous or homozygous for this mutation. 3 The protein product of the CF gene has been termed the CF transmembrane conductance regulator (CFfR). CFfR has not been isolated and characterized, but based on analysis of the eDNA for the CF gene and comparison of the sequence with other known proteins, it has been proposed that CFfR is a surface membrane glycoprotein with a large cytoplasmic portion. 4 The cytoplasmic portion has 2 putative nucleotide binding folds and a large domain of unknown function which has been called the R domain." Using antibodies generated to the R domain of CFfR, a protein Mr 165-170,000, the predicted size of CFfR, was detected in immortalized aitway epithelial cells from an *FroD! the Department of Pediatrics, University of Pennsylvania Me