9MUN | pdb_00009mun

Structure of Human SLC33A1 in complex with oxidized glutathione

• PDB DOI: https://doi.org/10.2210/pdb9MUN/pdb
• EM Map EMD-48638: EMDB EMDataResource

• Classification: TRANSPORT PROTEIN
• Organism(s): Homo sapiens
• Expression System: Homo sapiens
• Mutation(s): No 


• Deposited: 2025-01-14 Released: 2026-02-25 
• Deposition Author(s): Gad, M., Hite, R.K.
• Funding Organization(s): Other private

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Experimental Data Snapshot

• Method: ELECTRON MICROSCOPY
• Resolution: 3.26 Å
• Aggregation State: PARTICLE 
• Reconstruction Method: SINGLE PARTICLE 

Literature

SLC33A1 exports oxidized glutathione to maintain endoplasmic reticulum redox homeostasis.

Liu, S., Gad, M., Li, C., Cho, K., Liu, Y., Wangdu, K., Belay, V., Millet, A., Kojima, H., Sanford, H., Wolk, M., Urnavicius, L., Fedorova, M., Patti, G.J., Vinogradova, E.V., Hite, R.K., Birsoy, K.

(2026) Nat Cell Biol 28: 903-914

• PubMed: 41998286 
• DOI: https://doi.org/10.1038/s41556-026-01922-y
• Primary Citation Related Structures: 
  9MUN


• PubMed Abstract: 
  

  The endoplasmic reticulum (ER) requires an oxidative environment to support the efficient maturation of secretory and membrane proteins. This is in part established by glutathione, a redox-active metabolite present in reduced (GSH) and oxidized (GSSG) forms. The ER maintains a higher GSSG:GSH ratio than the cytosol; however, the mechanisms controlling ER redox balance remain poorly understood. To address this, we developed a method for the rapid immunopurification of the ER, enabling comprehensive profiling of its proteome and metabolome. Combining this approach with CRISPR screening, we identified SLC33A1 as the major ER GSSG exporter in mammalian cells. Loss of SLC33A1 led to GSSG accumulation in the ER and a liposome-based assay demonstrated that SLC33A1 directly transports GSSG. Cryogenic electron microscopy structures and molecular dynamics simulations revealed how SLC33A1 binds GSSG and identified residues critical for its transport. Finally, an imbalance in GSSG:GSH ratio induced ER stress and dependency on the ER-associated degradation pathway, driven by a shift in protein disulfide isomerases towards their oxidized forms. Together, our work establishes SLC33A1-mediated GSSG export as a key mechanism for ER redox homeostasis and protein maturation.

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Organizational Affiliation: 
• Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, New York, NY, USA.
Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
Department of Chemistry, Washington University, St Louis, MO, USA.
Center for Mass Spectrometry and Metabolic Tracing, Washington University, St Louis, MO, USA.
Siteman Cancer Center, Washington University School of Medicine, St Louis, MO, USA.
Center for Human Nutrition, Department of Medicine, Washington University School of Medicine, St Louis, MO, USA.
Physiology, Biophysics, and Systems Biology Program, Weill Cornell Graduate School of Biomedical Sciences, New York, NY, USA.
Computational and Systems Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
Laboratory of Systems Cancer Biology, The Rockefeller University, New York, NY, USA.
Laboratory of Chemical Immunology and Proteomics, The Rockefeller University, New York, NY, USA.
Center of Membrane Biochemistry and Lipid Research, University Hospital and Faculty of Medicine Carl Gustav Carus of Dresden University of Technology, Dresden, Germany.
Laboratory of Chemistry and Cell Biology, The Rockefeller University, New York, NY, USA.
Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA. [e-mail].
Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, New York, NY, USA. [e-mail].

Biological Assembly 1  

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Monomer - A1 

Biological assembly 1 assigned by authors.

Biological Assembly Evidence: electron microscopy

Macromolecule Content 

• Total Structure Weight: 62.77 kDa 
• Atom Count: 3,726 
• Modeled Residue Count: 471 
• Deposited Residue Count: 561 
• Unique protein chains: 1

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
Acetyl-coenzyme A transporter 1	A	561	Homo sapiens	Mutation(s): 0  Gene Names: SLC33A1, ACATN, AT1
UniProt & NIH Common Fund Data Resources
Find proteins for O00400 (Homo sapiens) Explore O00400  Go to UniProtKB:  O00400
PHAROS:  O00400 GTEx:  ENSG00000169359

Small Molecules

Ligands 1 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram
GDS (Subject of Investigation/LOI)	B [auth A]	OXIDIZED GLUTATHIONE DISULFIDE C20 H32 N6 O12 S2 YPZRWBKMTBYPTK-BJDJZHNGSA-N

Experimental Data & Validation

Experimental Data

• Method: ELECTRON MICROSCOPY
• Resolution: 3.26 Å
• Aggregation State: PARTICLE 
• Reconstruction Method: SINGLE PARTICLE 

EM Software:

Task	Software Package	Version
MODEL REFINEMENT	PHENIX	1.21.2_5419

Structure Validation

Entry History 

& Funding Information

Deposition Data

• Released Date: 2026-02-25 
Deposition Author(s): Gad, M., Hite, R.K.

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Funding Organization	Location	Grant Number
Other private		--

Revision History  

• Version 1.0: 2026-02-25
  Type: Initial release
  
• Version 1.1: 2026-05-13
  Changes: Data collection, Database references
• Version 1.2: 2026-05-27
  Changes: Data collection, Database references