Reversions partially restore gp120 folding. HeLa cells were infected with VVT7 and transfected with plasmids encoding mutant and revertant or wt gp120. Cells were pulse-labeled for 5 min. and chased for the indicated times. Cells were lysed and gp120 was immunoprecipitated from lysates. Immunoprecipitates were deglycosylated with endoH and analyzed by either reducing or nonreducing 7.5% SDS-PAGE. Folding intermediates (ITs), the native form (NT), the reduced state from which the signal peptide was cleaved off (Rc) or not (Ru) are indicated. In addition, secreted gp120 was immunoprecipitated from the culture supernatant after 8 hr chase and directly analyzed by reducing SDS-PAGE.