Kopcho N, Chang G, Komives EA. Dynamics of ABC Transporter P-glycoprotein in Three Conformational States.
Sci Rep 2019;
9:15092. [PMID:
31641149 PMCID:
PMC6805939 DOI:
10.1038/s41598-019-50578-2]
[Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 09/10/2019] [Indexed: 12/25/2022] Open
Abstract
We used hydrogen-deuterium exchange mass spectrometry (HDX-MS) to obtain a comprehensive view of transporter dynamics (85.8% sequence coverage) occurring throughout the multidrug efflux transporter P-glycoprotein (P-gp) in three distinct conformational states: predominantly inward-facing apo P-gp, pre-hydrolytic (E552Q/E1197Q) P-gp bound to Mg+2-ATP, and outward-facing P-gp bound to Mg+2-ADP-VO4−3. Nucleotide affinity was measured with bio-layer interferometry (BLI), which yielded kinetics data that fit a two Mg+2-ATP binding-site model. This model has one high affinity site (3.2 ± 0.3 µM) and one low affinity site (209 ± 25 µM). Comparison of deuterium incorporation profiles revealed asymmetry between the changes undergone at the critical interfaces where nucleotide binding domains (NBDs) contact intracellular helices (ICHs). In the pre-hydrolytic state, both interfaces between ICHs and NBDs decreased exchange to similar extents relative to inward-facing P-gp. In the outward-facing state, the ICH-NBD1 interface showed decreased exchange, while the ICH-NBD2 interface showed less of an effect. The extracellular loops (ECLs) showed reduced deuterium uptake in the pre-hydrolytic state, consistent with an occluded conformation. While in the outward-facing state, increased ECL exchange corresponding to EC domain opening was observed. These findings point toward asymmetry between both NBDs, and they suggest that pre-hydrolytic P-gp occupies an occluded conformation.
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