Fig. 6. Sec31B-F and Sec31A share the same intracellular distribution. (A) The distribution of full-length and truncated Sec31B was compared with endogenous Sec31A in Cos-7 cells. In all panels, endogenous wild-type Sec31A is stained red; Sec31B (wild-type or transfected) is stained green. Areas of coincidence appear yellow. (Top) Comparison of the endogenous proteins; overlap is extensive, but not complete. (Middle) Comparison of wt Sec31A with transfected eGYP-Sec31B-F; overlap is essentially complete. (Bottom) Comparison of wt Sec31A with transfected eGYP-Sec31B-T; notice the absence of any overlap. Arrows indicate discrete non-overlapping accumulations of Sec31A and Sec31B. (B) Lysates of the MDCK-787 cell line that stably expresses eYFP-Sec31B-F were immunoprecipitated with the antibody against Sec31A (kindly supplied by Fred Gorlick, Yale University). The precipitates were then probed for the presence of either eYFP-Sec31B-F (left panel) or for Sec31A (right panel). Non-immunesera was used as the control (ctrl). Notice that anti-Sec31A does not cross-react with eYFP-Sec31B-F.