A single amino acid substitution strongly modulates the activity and substrate specificity of the mouse mdr1 and mdr3 drug efflux pumps.
Specific protein domains and amino acids responsible for the apparent capacity of P-glycoprotein (mdr) to recognize and transport a large group of structurally unrelated drugs have not been identified. We have introduced a single Ser----Phe substitution within the predicted TM11 domain of mdr1 (position 941) and mdr3 (position 939) and analyzed the effect of these substitutions on the drug-resistance profiles of these two proteins. Mutations at this residue drastically altered the overall degree of drug resistance conveyed by mdr1 and mdr3. The modulating effect of this mutation on mdr1 and mdr3 varied for the drugs tested: it was very strong for colchicine and adriamycin and moderate for vinblastine. For mdr1, the Ser941----Phe941 substitution produced a unique mutant protein that retained the capacity to confer vinblastine resistance but lost the ability to confer adriamycin and colchicine resistance. These results strongly suggest that the predicted TM11 domain of proteins encoded by mdr and mdr-like genes plays an important role in the recognition and transport of their specific substrates.
Department of Biochemistry, McGill University, Montreal, PQ, Canada.
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D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D003078:Colchicine / Q000494:pharmacology; D006224:Cricetinae; D004317:Doxorubicin / Q000494:pharmacology; D004351:Drug Resistance / Q000235:genetics*; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D015345:Oligonucleotide Probes; D011487:Protein Conformation; D014162:Transfection; D014747:Vinblastine / Q000494:pharmacology
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D008562:Membrane Glycoproteins; D015345:Oligonucleotide Probes; D014747:Vinblastine; D004317:Doxorubicin; D003078:Colchicine