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| Title | Cryo-EM structure of a eukaryotic zinc transporter at a low pH suggests its Zn-releasing mechanism. |
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| Journal, issue, pages | J Struct Biol, Vol. 215, Issue 1, Page 107926, Year 2023 |
| Publish date | Dec 1, 2022 |
 Authors | Senfeng Zhang / Chunting Fu / Yongbo Luo / Qingrong Xie / Tong Xu / Ziyi Sun / Zhaoming Su / Xiaoming Zhou /  |
| PubMed Abstract | Zinc transporter 8 (ZnT8) is mainly expressed in pancreatic islet β cells and is responsible for H-coupled uptake (antiport) of Zn into the lumen of insulin secretory granules. Structures of human ...Zinc transporter 8 (ZnT8) is mainly expressed in pancreatic islet β cells and is responsible for H-coupled uptake (antiport) of Zn into the lumen of insulin secretory granules. Structures of human ZnT8 and its prokaryotic homolog YiiP have provided structural basis for constructing a plausible transport cycle for Zn. However, the mechanistic role that protons play in the transport process remains unclear. Here we present a lumen-facing cryo-EM structure of ZnT8 from Xenopus tropicalis (xtZnT8) in the presence of Zn at a luminal pH (5.5). Compared to a Zn-bound xtZnT8 structure at a cytosolic pH (7.5), the low-pH structure displays an empty transmembrane Zn-binding site with a disrupted coordination geometry. Combined with a Zn-binding assay our data suggest that protons may disrupt Zn coordination at the transmembrane Zn-binding site in the lumen-facing state, thus facilitating Zn release from ZnT8 into the lumen. |
 External links | J Struct Biol / PubMed:36464198 |
| Methods | EM (single particle) |
| Resolution | 3.72 - 3.85 Å |
| Structure data | EMDB-33619, PDB-7y5g: EMDB-33620, PDB-7y5h: |
| Chemicals |  ChemComp-ZN: |
| Source |
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 Keywords |  MEMBRANE PROTEIN / Zinc transporter / SLC30 / ZnT / CDF / Proton-coupled antiporter |
