title: The DrrAB efflux system of Streptomyces peucetius is a multidrug transporter of broad substrate specificity.
abstract: The soil bacterium Streptomyces peucetius produces two widely used anticancer antibiotics, doxorubicin and daunorubicin. Present within the biosynthesis gene cluster in S. peucetius is the drrAB operon, which codes for a dedicated ABC (ATP binding cassette)-type transporter for the export of these two closely related antibiotics. Because of its dedicated nature, the DrrAB system is believed to belong to the category of single-drug transporters. However, whether it also contains specificity for other known substrates of multidrug transporters has never been tested. In this study we demonstrate under both in vivo and in vitro conditions that the DrrAB system can transport not only doxorubicin but is also able to export two most commonly studied MDR substrates, Hoechst 33342 and ethidium bromide. Moreover, we demonstrate that many other substrates (including verapamil, vinblastine, and rifampicin) of the well studied multidrug transporters inhibit DrrAB-mediated Dox transport with high efficiency, indicating that they are also substrates of the DrrAB pump. Kinetic studies show that inhibition of doxorubicin transport by Hoechst 33342 and rifampicin occurs by a competitive mechanism, whereas verapamil inhibits transport by a non-competitive mechanism, thus suggesting the possibility of more than one drug binding site in the DrrAB system. This is the first in-depth study of a drug resistance system from a producer organism, and it shows that a dedicated efflux system like DrrAB contains specificity for multiple drugs. The significance of these findings in evolution of poly-specificity in drug resistance systems is discussed.
authors.affiliation: From the Department of Biology, Georgia State University, Atlanta, Georgia 30303.
authors.forename: Wen
authors.initials: W
authors.lastname: Li
authors.forename: Madhu
authors.initials: M
authors.lastname: Sharma
authors.forename: Parjit
authors.initials: P
authors.lastname: Kaur
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects / Q000235:genetics; D003630:Daunorubicin / Q000378:metabolism; D004317:Doxorubicin / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009154:Mutation; D012293:Rifampin / Q000378:metabolism / Q000494:pharmacology; D017386:Sequence Homology, Amino Acid; D013302:Streptomyces / Q000235:genetics / Q000378:metabolism*; D014638:Vanadates / Q000494:pharmacology; D014700:Verapamil / Q000378:metabolism / Q000494:pharmacology; D014747:Vinblastine / Q000378:metabolism / Q000494:pharmacology
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D003630:Daunorubicin; D004317:Doxorubicin; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D012293:Rifampin; D014638:Vanadates; D014700:Verapamil; D014747:Vinblastine; C104037:DrrA protein, Streptomyces peucetius; C104038:DrrB protein, Streptomyces peucetius
keywords: ABC Transporter; Anticancer Drug; Competitive Inhibition; Drug Binding Sites; Drug Resistance; Inside-out Membrane Vesicles; Multidrug Transporters; Non-competitive Inhibition; Protein Drug Interactions; Single-drug Transporters