FIG. 3.

SDS-polyacrylamide gel electrophoresis analysis of pseudotype viruses and immunoprecipitates of Sindbis gp from cell extracts. Pseudotype viruses were prepared in BHK-21 cells metabolically labeled for 48 h with [³⁵S]methionine and incubated at 32°C. Immunoprecipitates were prepared using VR1248, a mouse polyclonal antibody directed to the SV. The VSV proteins are used as molecular weight markers. The labeled lanes express either the initial or the adapted glycoprotein. The immunoprecipitates show 3 bands in the region of E2. The middle band represents the fully processed E2 found on the viral surface. The top band represents precursor E2 (PE2), and the bottom band represents either nonglycosylated E2 or an E2 breakdown product.