title: Characterization of the multidrug resistance protein expressed in cell clones stably transfected with the mouse mdr1 cDNA.
abstract: Structural features of the multidrug resistance protein encoded by the mouse mdr1 gene were studied in multidrug-resistant cell clones stably transfected with a biologically active cDNA clone. Independently derived transfectant cell clones, initially selected in Adriamycin, were shown to be cross-resistant to several drugs, including actinomycin D, amsacrine, mitoxantrone, VP-16, and vinblastine but remained sensitive to cis-platinum, 5-fluorouracil, arabinocytosine, and bleomycin. In drug-resistant transfectants the mdr1 gene product was greatly overexpressed as a polypeptide of apparent molecular weight 160,000-170,000. This protein was present in membrane enriched fractions and could be metabolically labeled with [3H )glucosamine, confirming that the transfected mdr1 gene encodes a membrane glycoprotein. The protein was found phosphorylated on serine residues and was shown to be photolabeled by both the calcium antagonist azidopine and the ATP analogue 8-azido ATP. Tryptic mapping of the ATP-photoaffinity labeled protein indicated that ATP crosslinking was site-specific and limited to two discrete peptide fragments of the protein, suggesting that the overexpressed mdr protein is capable of direct and specific ATP binding.
authors.affiliation: Department of Biochemistry, Faculty of Medicine, McGill University, Montreal, Canada.
authors.forename: E
authors.initials: E
authors.lastname: Schurr
authors.forename: M
authors.initials: M
authors.lastname: Raymond
authors.forename: J C
authors.initials: JC
authors.lastname: Bell
authors.forename: P
authors.initials: P
authors.lastname: Gros
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002460:Cell Line; D002999:Clone Cells; D006224:Cricetinae; D004247:DNA / Q000032:analysis*; D008562:Membrane Glycoproteins / Q000032:analysis* / Q000235:genetics; D010766:Phosphorylation; D014162:Transfection
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002121:Calcium Channel Blockers; D008562:Membrane Glycoproteins; D000255:Adenosine Triphosphate; D004247:DNA