Figure 4

Trypsin Sensitivity of CFTR PEST Mutants. Membranes were prepared from COS-1 cells transiently transfected with the cDNA of the various constructs. The membranes were treated with various concentrations (0–1000 μg/ml) of TPCK-treated trypsin. The reactions were stopped by the addition of lima bean trypsin inhibitor. Equivalent amounts of protein were subjected to immunoblot analysis (monoclonal antibody against the A52 tag).