FIG. 5.

Disruption of the disulfide linkage between gp70 and Pr15E after cell lysis depends on temperature and pH. Lysates of metabolically labeled amphotropic Mo-MLV env-expressing cells were prepared in the absence of alkylating agents, either at pH 7.5 (A and B) or at pH 6.0 (C). The lysates were incubated for the indicated times on ice (A and C) or at 37°C (B), after which NEM was added to 20 mM. The Env protein was thereafter immunoprecipitated with the polyclonal anti-MLV serum. Immunoprecipitates were analyzed in nonreducing SDS–12% polyacrylamide gels.