Figure 2.

Total cellular DAD1 cosediments with the OST subunits. Intact WI38 fibroblasts were solubilized in digitonin–high salt solution as described. The total homogenate (T) was centrifuged for 15 min at 160,000 × g to prepare a detergent-solubilized supernatant (S) and a detergent-insoluble pellet (P). The digitonin–high salt supernatant (S) was resolved by glycerol density gradient centrifugation into 14 fractions. Fraction 1 is the top of the gradient. Samples corresponding to 3% of the total homogenate, 3% of the supernatant, and 6% of the pellet were resolved on one polyacrylamide gel, and 18% of each gradient fraction was resolved on a second gel. Protein immunoblots used antibodies specific for ribophorins I (R I) and II (R II) and DAD1.