Figure 10.

Composition of E1-G_CT–containing membranes. BHK-E1-G_CT cells were homogenized and immunoisolates were prepared using P5D4 or BW8G65 as described above. Samples were subjected to SDS-PAGE on 10% gels and stained with Coomassie R-250. Protein molecular mass standards (kDa) are shown in lane 1. Only the portion of the gel above 30 kDa is shown, as only the IgG light bands were discernable in this region. The positions of known proteins are indicated. IgG Hc, IgG heavy chains. The IgG Hc region in both lanes is a doublet caused by the presence of secondary antibodies (P5D4 in lane 2, BW8G65 in lane 3) and primary antibody, goat anti-mouse IgG1, Fc-specific (both lanes). The P5D4 IgG Hc is the lowest band in the IgG Hc region, whereas the BW8G65 Hc migrates just below the goat anti-mouse IgG Hc. P5D4 immunoisolates contain a prominent 65-kDa protein (lane 2, arrow) of unknown identity that is not found in the nonspecific immunoisolate (lane 3). The asterisk in lane 2 denotes a 58-kDa protein that is thought to be p58/ERGIC53.