Effect of co-transfection with dominant negative mutants of SEC24. HEK293 cells were either transfected with p3xFLAG-CMV14/B0,+ vector or co-transfected with SEC24C-VN or SEC24D-VN, at ratio indicated in the figure. (A) Level of SEC24 proteins was analyzed by Western blot with the corresponding anti-SEC24 antibodies. Level of over-expressed ATB0,+ was analyzed with anti-FLAG antibodies. (B) The cells were biotinylated with membrane impermeable reagent and the biotinylated fraction, as well as total protein content were analyzed by Western blot with anti-FLAG antibodies. GAPDH was detected, as loading control.