Evidence for a Molecular Diode-based Mechanism in a Multispecific ATP-binding cassette (ABC) Exporter: SER-1368 AS A GATEKEEPING RESIDUE IN THE YEAST MULTIDRUG TRANSPORTER Pdr5* |
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| Authors: | Jitender Mehla Robert Ernst Rachel Moore Adina Wakschlag Mary Kate Marquis Suresh V. Ambudkar John Golin |
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| Affiliation: | From the ‡Department of Biology, Catholic University of America, Washington, D. C. 20064.;the §Institute of Biochemistry, Biocenter of the Goethe University, Frankfurt, Germany 60438, and ;the ¶Laboratory of Cell Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892 |
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| Abstract: | ATP-binding cassette multidrug efflux pumps transport a wide range of substrates. Current models suggest that a drug binds relatively tightly to a transport site in the transmembrane domains when the protein is in the closed inward facing conformation. Upon binding of ATP, the transporter can switch to an outward facing (drug off or drug releasing) structure of lower affinity. ATP hydrolysis is critically important for remodeling the drug-binding site to facilitate drug release and to reset the transporter for a new transport cycle. We characterized the novel phenotype of an S1368A mutant that lies in the putative drug-binding pocket of the yeast multidrug transporter Pdr5. This substitution created broad, severe drug hypersensitivity, although drug binding, ATP hydrolysis, and intradomain signaling were indistinguishable from the wild-type control. Several different rhodamine 6G efflux and accumulation assays yielded evidence consistent with the possibility that Ser-1368 prevents reentry of the excluded drug. |
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| Keywords: | ABC Transporter ATPase Drug Transport Membrane Protein Multidrug Transporter |
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