Figure 3.

The W1282X CFTR chimera exhibits lower detergent solubility and oligomerizes in the ER membrane. (A) The solubility of the WT, N1303K, and W1282X CFTR chimeras in ER‐derived microsomes was examined in the presence of buffer (0 mM), 0.5 mM DDM, or 1% SDS. (B) Quantification of the results of the solubility assay, as performed in part (A), based on an analysis of four to six independent experiments, ±SEM. (C) A schematic of the flotation assay used to measure the oligomerization of membrane proteins.41 (D, E) LYSATES from WT yeast expressing the designated chimeras, and WT CFTR were prepared and analyzed by sucrose density centrifugation. Gradient samples were processed and immunoblotted against the HA tag to detect protein residence. The quantification of experiments with the (D) N1303K stable CFTR chimera and the (E) W1282X unstable chimera are shown. For comparison, the fractionation of the WT species (closed circles) is reproduced in both panels. Data were standardized to the amount of protein in each gradient fraction relative to the total from four independent experiments, ±SEM.