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Nat Struct Mol Biol. 2016 Mar;23(3):256-63. doi: 10.1038/nsmb.3166. Epub 2016 Feb 1.

The bacterial dicarboxylate transporter VcINDY uses a two-domain elevator-type mechanism.

Author information

1
Membrane Transport Biophysics Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA.
2
Computational Structural Biology Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA.
3
Max Planck Institute of Biophysics, Frankfurt am Main, Germany.
4
Protein/Peptide Sequencing Facility, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA.

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.

PMID:
26828963
PMCID:
PMC5215794
DOI:
10.1038/nsmb.3166
[Indexed for MEDLINE]
Free PMC Article

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