Fig. 8. Both the banding pattern of cysteine proteinase activity from purified phagosomes and the banding pattern of a western blot decorated with an antibody to GlcNac-1-P suggest that immature cysteine proteinases are delivered to phagosomes in cells overexpressing DN Rab7. (A) Proteins from phagosomes purified from control cells and cells overexpressing DN Rab7 were separated by SDS-PAGE on gels made with 0.2% gelatin. Phagosomes were formed by pulsing cells with latex beads for 30 minutes. Cysteine proteinase activity was visualized as described in Materials and Methods. + indicates samples that were pre-incubated with E-64. H, whole cell homogenate; P, phagosomes; X4, control and 7TN, DN Rab7 overexpressors. (B) Western blots of whole cell lysates and purified phagosomes from control cells and cells overexpressing DN Rab7 were made using the GlcNac-1-P-recognizing antibody AD7.5. Phagosomes were formed by pulsing cells with latex beads for 30 minutes. Abbreviations as for A. The positions of marker proteins (kDa) are shown.