FIG. 4.

GP₀ cannot be dissociated from virions by denaturation or reduction. MLV(Ebo-GP) (A) and MLV(Ebo-GP.CL(−) (B) were produced by transient transfection of 293T cells. Forty-eight hours posttransfection, virion-containing cellular supernatants were collected and partially purified through 20% sucrose. The resulting viral pellets were resuspended in PBS and treated with the indicated concentrations of urea, with (+) or without (−) 100 mM DTT. These treated virions were then partially purified by pelleting through 20% sucrose, lysed, and analyzed by SDS-PAGE and Western blotting with the anti-Ebo-GP serum. Arrows indicate GP₁ and GP₀; positions of molecular mass markers (in kilodaltons) are shown to the left of each gel.