Surface expression of murine leukemia virus structural polypeptides on host cells and the virion.

The expression of murine leukemia virus structural polypeptides on the surface of cells producing exogenous Friend leukemia virus, endogenous ecotropic AKR and xenotropic BALB/c virus was investigated. Antisera to Friend virus gp71, p30, p15E, p12 and p10 were employed in a complement-dependent chromium release assay and to immunoprecipitate lactoperoxidase iodinated surface polypeptides prior to analysis in polyacrylamide gel electrophoresis. With the latter technique gag-gene encoded proteins and their precursors were not discovered on the viral and cellular surface membranes. Only env-gene encoded polypeptides gp85, gp71, and p15E were detectable. p15E is embedded into the lipid membrane. gp85 is formed by disulfide linkage of p15E to surface-exposed gp71. The ratio of gp71 to gp85 is variable and apparently determined by the host cell. Antibodies of strong cytotoxicity are those against type- and group-specific epitopes of gp71 as well as type-specific epitopes of p12.