title: The bacterial dicarboxylate transporter VcINDY uses a two-domain elevator-type mechanism.
abstract: Secondary transporters use alternating-access mechanisms to couple uphill substrate movement to downhill ion flux. Most known transporters use a 'rocking bundle' motion, wherein the protein moves around an immobile substrate-binding site. However, the glutamate-transporter homolog GltPh translocates its substrate-binding site vertically across the membrane, through an 'elevator' mechanism. Here, we used the 'repeat swap' approach to computationally predict the outward-facing state of the Na(+)/succinate transporter VcINDY, from Vibrio cholerae. Our model predicts a substantial elevator-like movement of VcINDY's substrate-binding site, with a vertical translation of ~15 Å and a rotation of ~43°. Our observation that multiple disulfide cross-links completely inhibit transport provides experimental confirmation of the model and demonstrates that such movement is essential. In contrast, cross-links across the VcINDY dimer interface preserve transport, thus revealing an absence of large-scale coupling between protomers.
authors.affiliation: Membrane Transport Biophysics Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Mulligan
authors.affiliation: Computational Structural Biology Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA.|Max Planck Institute of Biophysics, Frankfurt am Main, Germany.
authors.forename: Cristina
authors.initials: C
authors.lastname: Fenollar-Ferrer
authors.affiliation: Membrane Transport Biophysics Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Gabriel A
authors.initials: GA
authors.lastname: Fitzgerald
authors.affiliation: Computational Structural Biology Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Ariela
authors.initials: A
authors.lastname: Vergara-Jaque
authors.affiliation: Max Planck Institute of Biophysics, Frankfurt am Main, Germany.
authors.forename: Desirée
authors.initials: D
authors.lastname: Kaufmann
authors.affiliation: Protein/Peptide Sequencing Facility, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.affiliation: Computational Structural Biology Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Lucy R
authors.identifier: http://orcid.org/0000-0003-1855-7985
authors.initials: LR
authors.lastname: Forrest
authors.affiliation: Membrane Transport Biophysics Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Mindell
mesh_terms: D029382:Dicarboxylic Acid Transporters / Q000737:chemistry* / Q000378:metabolism*; D008954:Models, Biological; D008956:Models, Chemical; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D014734:Vibrio cholerae / Q000201:enzymology*
chemical_list: D029382:Dicarboxylic Acid Transporters
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