FIG. 5.

The TM domain of SFV E1 does not bind [³H]photocholesterol. The SFV envelope proteins E1 and E2 were reconstituted by detergent dialysis into liposomes containing [³H]photocholesterol. Protein-free [³H]photocholesterol-labeled liposomes were prepared in parallel by detergent dialysis and then mixed with E1′. The protein-liposome mixtures were treated at the indicated pH for 30 min at 25°C. (A) Liposome coflotation of SFV E1′ versus reconstituted full-length (FL) E1. Aliquots of the samples were tested for liposome association as described for Fig. 4B. The increase in FL E1 in the top of the gradient after low pH treatment may reflect fusion between proteoliposomes leading to more efficient flotation. (B) Photoaffinity labeling of SFV E1′ versus reconstituted full-length E1. Aliquots of the samples were exposed to UV light and analyzed for photocholesterol labeling as for Fig. 4D. The positions of SFV E1′ and SFV E1 are indicated based on parallel Western blot analysis. Panels A and B are representative examples of two independent experiments.