FIG. 6.

Membrane topology of the GP₃ protein. ORF3 RNA transcripts were translated in vitro in the presence of canine pancreatic microsomes. Subsequently, the translation products were treated or mock treated with proteinase K (prot. K) in the absence of detergent or after disruption of the microsomal membranes with TX-100. After a 1-h incubation at 4°C, the proteinase K was inactivated by protease inhibitors. Next, the samples were immunoprecipitated with a GP₃-specific antipeptide serum (GP₃) or its preimmune serum (pGP₃). The resulting immune complexes were each split into two equal portions that were treated or mock treated with PNGase F. The samples were dissolved in LSB containing 5% β-mercaptoethanol and analyzed in SDS-15% PAA gels. The values on the left are the molecular sizes, in kilodaltons, of marker proteins analyzed in the same gel. Ab, antibody.