FIGURE 8.

Schematic presentation of the membrane topology and processing scheme of the pestivirus polyprotein region encompassing E^rns, E1, and the N-terminal part of E2 (not drawn to scale). Transmembrane regions and the E^rns C-terminal amphipathic helix are shown as cylinders, whereas the rest of the proteins are indicated by black lines. The two gray horizontal lines represent the ER- or cytosol-facing surfaces of the ER membrane. The translocon is indicated as a light gray structure. SPase cleavage sites are marked by arrows and SPase. The signal sequence upstream of E^rns responsible for E^rns translocation is not shown. Note that the transmembrane region upstream of the E2 protein is a regular signal sequence with a typical transmembrane topology that stands in marked contrast to the in plane configuration of the E^rns amphipathic helix preceding the E^rns/E1 SPase cleavage site.