Fig. 3. Rabaptin-5α and γ-adaptin co-localize to tubulo-vesicular membrane clusters. Ultrathin cryosections of HeLa cells transfected with rabaptin- 5α-pcDNA3.1His (A,C and E) or with rabaptin-5α and γ₁-adaptin-pcDNA3 (B and D). Double labelling of rabaptin-5α (10 nm gold) and γ₁-adaptin (15 nm gold). Rabaptin-5α is associated with clusters of vesicular tubular membranes, where it co-localized with endogenous (A) and overexpressed γ₁-adaptin (B). The overall density and diameter of rabaptin-5α-positive membranes is reminiscent of recycling tubules. The dense cytosol between the membranes indicates the presence of high concentrations of cytosolic protein. Note that some of the membranes display a coating typical of the presence of clathrin (arrows in A and B). Double labelling of TGN46 (15 nm gold) and rabaptin-5α (10 nm gold) revealed that rabaptin-5α-positive membranes do not overlap with TGN membranes (C). Rabaptin-5α- (15 nm gold) positive membranes do not contain internalized BSA–5 nm gold. Arrows point to compartments that contain the endocytic marker 10 min after internalization (D). Double labelling of rabaptin-5α (15 nm gold) and clathrin (10 nm gold). Some of the membranes within or associated with rabaptin-5α-positive membranes also stained for clathrin (arrows). Note that the nearby endosomal vacuole (E) has a normal morphology (E). G = Golgi complex, L = lysosome. Bar, 200 nm.