Western blotting of ABC transport proteins in virus producing cells. Lysates of 293T cells producing lentiviralvectors with or without co-transfection of ABC transporters were subjected to western blotting as described. Lanes represent: (1) wild type ABCB4, (2) mutant ABCB4, (3) negative control and (4) ABCC1. Wild type and mutant ABCB4 migrated at an apparent molecular mass of 140 kDa. ABCC1 migrated at a molecular mass of 170 kD. The two bands in both ABCB4 and ABCC1 lanes most likely correspond to differently glycosylated forms. Wild type and mutant ABCB4 appear to be differently processed. Similar amounts of cellular protein were loaded as shown by β-actin antibody reactivity.