Figure 4. Most of the RTB was retained in the early secretory pathway from where it disappeared with time.

(A) Pulse-labelled RTB (black arrowhead) from cell extracts and conditioned medium was immunoprecipitated after chase (t) for up to 12 h, and electrophoresed under reducing conditions. (B) Immunoprecipitates, as generated in (A), were incubated with or without endo H as described in the Materials and methods section. Such a treatment generated a faster migrating form (open arrowhead) that co-migrated with the Tn-treated samples. (C) RTB, recovered by immunoprecipitation from conditioned growth medium (black arrowhead), was treated with endo H to generate two faster migrating species (open and grey arrowheads). (D) Cells treated with BFA were lysed and RTB immunoprecipitated from cell and media fractions. Molecular-mass standards are shown on the left (A–C) or right (D).