ABSTRACT
In mammals, four ATP-binding cassette (ABC) proteins belonging to subfamily D have been identified. ABCD1â3 are located on peroxisomal membrane and play an important role in the transportation of various fatty acid-CoA derivatives, including very long chain fatty acid-CoA, into peroxisomes. ABCD4 is located on lysosomal membrane and is suggested to be involved in the transport of vitamin B12 from lysosomes to the cytosol. However, the precise transport mechanism by which these ABC transporters facilitate the import or export of substrate has yet to be well elucidated. In this study, the overexpression of human ABCD1â4 in the methylotrophic yeast Pichia pastoris and a purification procedure were developed. The detergent-solubilized proteins were reconstituted into liposomes. ABCD1â4 displayed stable ATPase activity, which was inhibited by AlF3. Furthermore, ABCD1â4 were found to possess an equal levels of acyl-CoA thioesterase activity. Proteoliposomes is expected to be an aid in the further biochemical characterization of ABCD transporters.