Amino acid substitutions in the sixth transmembrane domain of P-glycoprotein alter multidrug resistance.
Eukaryotic cells can display resistance to a wide range of natural-product chemotheraputic agents by the expression of P-glycoprotein (pgp), a putative plasma membrane transporter that is thought to mediate the efflux of these agents from cells. We have identified, in cells selected for multidrug resistance with actinomycin D, a mutant form of pgp that contains two amino acid substitutions within the putative sixth transmembrane domain. In transfection experiments, this altered pgp confers a cross-resistance phenotype that is altered significantly from that conferred by the normal protein, displaying maximal resistance to actinomycin D. These results strongly implicate the sixth transmembrane domain in the mechanism of pgp drug recognition and efflux. Moreover, they indicate a close functional homology between pgp and the cystic fibrosis transmembrane regulator in which the sixth transmembrane domain has also been shown to influence substrate specificity.
Department of Biological Chemistry, University of Maryland School of Medicine, Baltimore 21201.
S E
SE
Devine
V
V
Ling
P W
PW
Melera
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D006224:Cricetinae; D003609:Dactinomycin / Q000494:pharmacology; D004351:Drug Resistance / Q000502:physiology*; D015870:Gene Expression; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics / Q000502:physiology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides; D010957:Plasmids; D016133:Polymerase Chain Reaction / Q000379:methods; D011487:Protein Conformation; D012333:RNA, Messenger / Q000235:genetics; D014162:Transfection
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D008562:Membrane Glycoproteins; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D003609:Dactinomycin