Abstract
The multidrug transporter P-glycoprotein (P-gp, ABCB1) is an ATP-dependent efflux pump that mediates the efflux of structurally diverse drugs and xenobiotics across cell membranes, affecting drug pharmacokinetics and contributing to the development of multidrug resistance. Structural information about the conformational changes in human P-gp during the ATP hydrolysis cycle has not been directly demonstrated, although mechanistic information has been inferred from biochemical and biophysical studies done with P-gp and its orthologs, or from structures of other ABC transporters. Using single particle cryo-electron microscopy, we report the surprising discovery that, in the absence of the transport substrate and nucleotides, human P-gp can exist in both open (nucleotide-binding-domains (NBDs) apart; inward-facing) and closed (NBDs close; outward-facing) conformations. We also probe conformational states of human P-gp during the catalytic cycle, and demonstrate that following ATP hydrolysis, P-gp transitions through a complete closed conformation to a complete open conformation in the presence of ADP.
- The American Society for Pharmacology and Experimental Therapeutics