Figure 1.

Cosedimentation of DAD1 with OST activity, ribophorins I and II, and OST48. (A) A digitonin–high salt extract prepared from DK-RM was resolved by preparative glycerol density gradient centrifugation. Fraction 1 is the top of the gradient. Duplicate aliquots from each of 14 gradient fractions were assayed for OST activity. (B) Aliquots from each gradient fraction were analyzed on protein immunoblots using antibodies to ribophorin I (R I), ribophorin II (R II), OST48, and DAD1. The 64-kDa-glycosylated and 63-kDa-nonglycosylated forms of ribophorin II migrate as a doublet (13).