Fig. 7. Surface transferrin receptor measurements. Ligand binding studies were performed as described in the Materials and Methods. Briefly, control cells transfected with the vector alone (white bar) or with Rab11 wt (black bar) or mutants (hatched bars) were incubated with increasing concentrations of ¹²⁵I-transferrin for 90 minutes at 4°C. Cells were washed, and binding was determined by spinning the cells through dibutyl phthalate oil. Nonspecific binding was determined and subtracted for each point. Specific binding data were analyzed by the Scatchard method to determine the number of Tf-binding sites. The data represent the mean±s.e.m. of four independent experiments. Statistical analysis: t-test for single group mean. ^*Mean differs from control P<0.05; ^**mean differs from control P<0.01.