ABCB1, also known as P-glycoprotein, actively extrudes xenobiotic compounds across the plasma membrane of diverse cells, which contributes to cellular drug resistance and interferes with therapeutic drug delivery. We determined the 3.5-angstrom cryo–electron microscopy structure of substrate-bound human ABCB1 reconstituted in lipidic nanodiscs, revealing a single molecule of the chemotherapeutic compound paclitaxel (Taxol) bound in a central, occluded pocket. A second structure of inhibited, human-mouse chimeric ABCB1 revealed two molecules of zosuquidar occupying the same drug-binding pocket. Minor structural differences between substrate- and inhibitor-bound ABCB1 sites are amplified toward the nucleotide-binding domains (NBDs), revealing how the plasticity of the drug-binding site controls the dynamics of the adenosine triphosphate–hydrolyzing NBDs. Ordered cholesterol and phospholipid molecules suggest how the membrane modulates the conformational changes associate with drug binding and transport.
Bibliographical noteFunding Information:
We thank the staff at the Scientific Center for Optical and Electron Microscopy (SCOPEM) at ETH Zürich. We also acknowledge N. Tremp for help with protein expression and cell culture work. Funding: This work was funded by the European Molecular Biology Organization long-term postdoctoral fellowship to A.A., grants from the Swiss Cancer League to K.P.L., the Swiss National Science Foundation through NCCR Structural Biology and TransCure, the Swiss Cancer League, and U.S. National Institutes of Health grant P20GM109091 to E.B. and I.R.
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- ATP Binding Cassette Transporter, Subfamily B/antagonists & inhibitors
- Adenosine Triphosphate/chemistry
- Antineoplastic Agents, Phytogenic/chemistry
- Binding Sites
- Cryoelectron Microscopy
- Drug Design
- Mutant Chimeric Proteins/antagonists & inhibitors
- Protein Binding
- Protein Domains/drug effects
- Substrate Specificity
PubMed: MeSH publication types
- Research Support, Non-U.S. Gov't
- Journal Article
- Research Support, N.I.H., Extramural