Cryo-EM structures of human ZnT8 in both outward- and inward-facing conformations

  1. Jing Xue
  2. Tian Xie
  3. Weizhong Zeng
  4. Youxing Jiang  Is a corresponding author
  5. Xiao-chen Bai  Is a corresponding author
  1. University of Texas Southwestern Medical Center, United States

Abstract

ZnT8 is a Zn2+/H+ antiporter that belongs to SLC30 family and plays an essential role in regulating Zn2+ accumulation in the insulin secretory granules of pancreatic β cells. Dysfunction of ZnT8 is associated with both type 1 and 2 diabetes. However, the Zn2+/H+ exchange mechanism of ZnT8 remains unclear due to the lack of high-resolution structures. Here, we report the cryo-EM structures of human ZnT8 (HsZnT8) in both outward- and inward-facing conformations. HsZnT8 forms a dimeric structure with four Zn2+ binding sites within each subunit: a highly conserved primary site in transmembrane domain (TMD) housing the Zn2+ substrate; an interfacial site between TMD and C-terminal domain (CTD) that modulates the Zn2+ transport activity of HsZnT8; and two adjacent sites buried in the cytosolic domain and chelated by conserved residues from CTD and the His-Cys-His (HCH) motif from the N-terminal segment of the neighboring subunit. A comparison of the outward- and inward-facing structures reveals that the TMD of each HsZnT8 subunit undergoes a large structural rearrangement, allowing for alternating access to the primary Zn2+ site during the transport cycle. Collectively, our studies provide the structural insights into the Zn2+/H+ exchange mechanism of HsZnT8.

Data availability

The Cryo-EM maps of HsZnT8 determined in three different conditions will have been deposited in the Electron Microscopy Data Bank and. The corresponding atomic coordinates will be deposited to the RCSB Protein Data Bank, with the entry ID: EMD-22285 and PDB 6XPD for the structure of HsZnT8-DM, EMD-22286 and PDB 6XPE for the structure of HsZnT8-WT in the presence of zinc, and EMD-22287 and PDB 6XPF for the structure of HsZnT8-WT in the absence of zinc. Source data files have been provided for Figure 2h and 2i.

The following previously published data sets were used

Article and author information

Author details

  1. Jing Xue

    Department of Physiology, University of Texas Southwestern Medical Center, Dallas, United States
    Competing interests
    The authors declare that no competing interests exist.
  2. Tian Xie

    Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
    Competing interests
    The authors declare that no competing interests exist.
  3. Weizhong Zeng

    Department of Physiology, University of Texas Southwestern Medical Center, Dallas, United States
    Competing interests
    The authors declare that no competing interests exist.
  4. Youxing Jiang

    Department of Physiology, University of Texas Southwestern Medical Center, Dallas, United States
    For correspondence
    youxing.jiang@utsouthwestern.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-1874-0504
  5. Xiao-chen Bai

    Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
    For correspondence
    Xiaochen.Bai@UTSouthwestern.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-4234-5686

Funding

National Institute of General Medical Sciences (R01GM136976)

  • Xiao-chen Bai

Welch Foundation (I-1944)

  • Xiao-chen Bai

Cancer Prevention and Research Institute of Texas (RP160082)

  • Xiao-chen Bai

Howard Hughes Medical Institute

  • Youxing Jiang

National Institute of General Medical Sciences (GM079179)

  • Youxing Jiang

Welch Foundation (I-1578)

  • Youxing Jiang

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Olga Boudker, Weill Cornell Medicine, United States

Version history

  1. Received: May 12, 2020
  2. Accepted: July 28, 2020
  3. Accepted Manuscript published: July 29, 2020 (version 1)
  4. Version of Record published: August 14, 2020 (version 2)

Copyright

© 2020, Xue 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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  1. Jing Xue
  2. Tian Xie
  3. Weizhong Zeng
  4. Youxing Jiang
  5. Xiao-chen Bai
(2020)
Cryo-EM structures of human ZnT8 in both outward- and inward-facing conformations
eLife 9:e58823.
https://doi.org/10.7554/eLife.58823

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https://doi.org/10.7554/eLife.58823

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