- EMDB-33620: Cryo-EM structure of a eukaryotic ZnT8 at a low pH -
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Basic information
Entry
Database: EMDB / ID: EMD-33620
Title
Cryo-EM structure of a eukaryotic ZnT8 at a low pH
Map data
Sample
Complex: xtZnT8 dimer complexed with zinc and proton
Protein or peptide: Zinc transporter 8
Ligand: ZINC ION
Function / homology
Function and homology information
Insulin processing / Zinc efflux and compartmentalization by the SLC30 family / : / zinc ion transmembrane transporter activity / zinc ion transmembrane transport / intracellular zinc ion homeostasis / insulin secretion / transport vesicle membrane / response to zinc ion / response to glucose ...Insulin processing / Zinc efflux and compartmentalization by the SLC30 family / : / zinc ion transmembrane transporter activity / zinc ion transmembrane transport / intracellular zinc ion homeostasis / insulin secretion / transport vesicle membrane / response to zinc ion / response to glucose / membrane => GO:0016020 / plasma membrane Similarity search - Function
National Natural Science Foundation of China (NSFC)
31770783
China
Citation
Journal: J Struct Biol / Year: 2023 Title: Cryo-EM structure of a eukaryotic zinc transporter at a low pH suggests its Zn-releasing mechanism. Authors: Senfeng Zhang / Chunting Fu / Yongbo Luo / Qingrong Xie / Tong Xu / Ziyi Sun / Zhaoming Su / Xiaoming Zhou / 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.
Cryogen name: ETHANE / Chamber humidity: 100 % / Chamber temperature: 283 K / Instrument: FEI VITROBOT MARK IV / Details: blot for 2-3 s before plunging.
Details
This sample was monodisperse.
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Electron microscopy
Microscope
FEI TITAN KRIOS
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
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