Fig. 8. Localization of Shiga toxin and CHC in Myc-Rab5^Q79L-transfected cells. HeLa (A) and BHK (B) control cells grown in the presence of tetracycline were transfected with a GTPase-deficient mutant form of Rab5 (Myc-Rab5^Q79L) to induce the formation of enlarged early endosomes (EE). The cells were further grown with (+ ba) or without (–ba) butyric acid for 24 hours before incubation with 1 µg ml^–1 Alexa Fluor 488-labelled Shiga toxin (STx) for 20 minutes. CHC staining was performed by using goat anti-CHC antibodies followed by rhodamine-labelled donkey anti-goat IgG. The enlarged endosomes in transfected cells were identified with mouse anti-Myc antibodies followed by CY5-labelled donkey anti-mouse IgG. The white squares to the left are shown in enlarged versions to the right (green and red channels alone and the merged picture). The graphs show quantification of the extent of colocalization between STx and CHC on EE (as the percentage of the total amount of toxin) of 6-11 endosomes from four to six cells. The error bars represent the standard error of the mean.