Figure 6.

A small molecule passes into the ER but not into lysosomes or the trans-Golgi. HeLa cells (2 × 10⁶) were permeabilized with SLO, 0.04% digitonin (Dig), or 0.1% digitonin as indicated. Then 0.5 mM sulfo-NHS-LC-biotin was added for 30 min on ice. After solubilization in detergent, cell lysates were incubated with streptavidin agarose beads, and the bound material was analyzed by SDS-PAGE and immunoblotting with antibodies to various proteins. Hex B, hexosaminidase B; Cath D, cathepsin D; βGT1; β-1,4-galactosyl transferase. For βGT1, twice as much sample was used. Cell lysate corresponding to 10% of the input material was loaded as a control (lane 1).