Figure 1.

Retrotranslocation of the CTA1 subunit. (A) HeLa cells were incubated with CT for 90 min at 4 or 37°C with or without BFA or NEM. Cells were permeabilized, centrifuged, and the supernatant and pellet fractions were separated, subjected to nonreducing SDS-PAGE, and immunoblotted with the indicated antibodies. CTA, CTA1, and CTB are 28, 22, and 11 kD, respectively. (B) As in A except a CT mutant, R192H, was used. PDI is 58 kD. (C) As in A except where indicated, cells were treated with MG132. Polyubiquitinated proteins range from 100 to 300 kD. White lines indicate that intervening lanes have been spliced out.