(A) Representative confocal fluorescence micrographs of HeLa cells transfected for 24 h to produce either mCherry or mCherry-BspF (grayscale panels), incubated on ice with AlexaFluor™488-Cholera Toxin subunit B (CTxB; green) and shifted to 37˚C for 20 min to allow for CTxB retrograde transport to the Golgi apparatus (stained using an anti-GM130 antibody; purple). CTxB accumulation within Golgi structures appears white in overlays. Scale bars: 10 and 2 µm (insets). (B) Quantification of CTxB transport to the Golgi apparatus in HeLa cells producing either mCherry, mCherry-BspF or HA-BspF over a 30 min time course, expressed as percentages of cells in which CTxB colocalized with the GM130 Golgi marker, as in (A). Data are means ± SD from n=3 independent experiments, in which 100 cells were analyzed per experiment. Asterisks indicate statistically significant differences compared to mCherry-producing cells as determined by a two-way ANOVA with Tukey's multiple comparisons test (P<0.05). ( 