Structural basis for the reaction cycle of DASS dicarboxylate transporters
- New York University School of Medicine, United States
- University of Illinois at Urbana-Champaign, United States
- University of Illinoi Urbana-Champaign, United States
Abstract
Citrate, α-ketoglutarate and succinate are TCA cycle intermediates that also play essential roles in metabolic signaling and cellular regulation. These di- and tricarboxylates are imported into the cell by the divalent anion sodium symporter (DASS) family of plasma membrane transporters, which contains both cotransporters and exchangers. While DASS proteins transport substrates via an elevator mechanism, to date structures are only available for a single DASS cotransporter protein in a substrate-bound, inward-facing state. We report multiple cryo-EM and X-ray structures in four different states, including three hitherto unseen states, along with molecular dynamics simulations, of both a cotransporter and an exchanger. Comparison of these outward- and inward-facing structures reveal how the transport domain translates and rotates within the framework of the scaffold domain through the transport cycle. Additionally, we propose that DASS transporters ensure substrate coupling by a charge-compensation mechanism, and by structural changes upon substrate release.
Data availability
Cryo-EM maps and models have been deposited in the Protein Data Bank and EMDB database, respectively, for VcINDY-Na+ in amphipol (6WU3, EMD-21904), VcINDY-Na+-Fab84 in nanodisc (6WW5, EMD-21928), LaINDY-apo (6WU1, EMD-21902), LaINDY-aKG (6WU4, EMD-21905), and LaINDY-malate (6WU2, EMD-21903). X-ray derived models and diffraction data have been deposited in the Protein Data Bank for LaINDY-malate-aKG (6WTW) and VcINDY-TTP (6WTX). Coordinates of representative LaINDY structures from MD simulations of the Co-S and Ci-S states will be made publicly available on Zenodo (DOI: 10.5281/zenodo.3965996). Bond length analysis code is available at https://github.com/DavidBSauer/bond_length_analysis.
Article and author information
Author details
Funding
National Institutes of Health (R01NS108151)
- Da-Neng Wang
Department of Defense (W81XWH-16-1-0153)
- David B Sauer
National Science Foundation (1746047)
- Noah Trebesch
National Institutes of Health (T32GM088118)
- Nicolette Cocco
Blue Waters and XSEDE (TG-MCA06N060)
- Emad Tajkhorshid
National Institutes of Health (R01GM121994)
- Da-Neng Wang
National Institutes of Health (R01DK099023)
- Da-Neng Wang
National Institutes of Health (U54GM095315)
- Da-Neng Wang
National Institutes of Health (P41GM104601)
- Emad Tajkhorshid
National Institutes of Health (R01GM067887)
- Emad Tajkhorshid
TESS Research Foundation
- Da-Neng Wang
American Epilepsy Society (AES2017SD3)
- Da-Neng Wang
American Cancer Society (129844-PF-17-135-01-TBE)
- David B Sauer
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2020, Sauer et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Structural basis for the reaction cycle of DASS dicarboxylate transporters
eLife 9:e61350.
https://doi.org/10.7554/eLife.61350
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