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- EMDB-64369: Cryo-EM structure of human organic solute transporter Ost-alpha/b... -

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Basic information

Entry
Database: EMDB / ID: EMD-64369
TitleCryo-EM structure of human organic solute transporter Ost-alpha/beta bound with DHEAS
Map data
Sample
  • Complex: Heterodimer of Ost alpha and Ost beta
    • Protein or peptide: Organic solute transporter subunit alpha
    • Protein or peptide: Organic solute transporter subunit beta
  • Ligand: (7E,21R,24S)-27-amino-24-hydroxy-18,24-dioxo-19,23,25-trioxa-24lambda~5~-phosphaheptacos-7-en-21-yl (9Z,12E)-octadeca-9,12-dienoate
  • Ligand: PHOSPHATIDYL ETHANOL
  • Ligand: 1-O-OCTADECYL-SN-GLYCERO-3-PHOSPHOCHOLINE
  • Ligand: CHOLESTEROL
  • Ligand: PALMITIC ACID
  • Ligand: 17-oxoandrost-5-en-3beta-yl hydrogen sulfate
  • Ligand: water
Keywordssubstrate / transport / heterodimer / TRANSPORT PROTEIN
Function / homology
Function and homology information


bile acid secretion / positive regulation of glycoprotein biosynthetic process / positive regulation of protein exit from endoplasmic reticulum / bile acid transmembrane transporter activity / bile acid and bile salt transport / positive regulation of protein targeting to membrane / transmembrane transporter activity / Recycling of bile acids and salts / regulation of protein stability / basolateral plasma membrane ...bile acid secretion / positive regulation of glycoprotein biosynthetic process / positive regulation of protein exit from endoplasmic reticulum / bile acid transmembrane transporter activity / bile acid and bile salt transport / positive regulation of protein targeting to membrane / transmembrane transporter activity / Recycling of bile acids and salts / regulation of protein stability / basolateral plasma membrane / protein heterodimerization activity / endoplasmic reticulum membrane / protein homodimerization activity / protein-containing complex / membrane / plasma membrane
Similarity search - Function
Organic solute transporter subunit beta / : / Organic solute transporter subunit beta protein / Organic solute transporter subunit alpha/Transmembrane protein 184 / Organic solute transporter Ostalpha / Organic solute transporter Ostalpha
Similarity search - Domain/homology
Organic solute transporter subunit alpha / Organic solute transporter subunit beta
Similarity search - Component
Biological speciesHomo sapiens (human)
Methodsingle particle reconstruction / cryo EM / Resolution: 2.9 Å
AuthorsYang X / Xu E
Funding support China, 1 items
OrganizationGrant numberCountry
National Natural Science Foundation of China (NSFC) China
CitationJournal: Nature / Year: 2026
Title: Structures of Ostα/β reveal a unique fold and bile acid transport mechanism.
Authors: Xuemei Yang / Nana Cui / Tianyu Li / Xinheng He / Heng Zhang / Canrong Wu / Yang Li / Xiong Ma / H Eric Xu /
Abstract: Bile acid and steroid hormone homeostasis are critical for human health, with disruptions linked to metabolic and endocrine disorders. The organic solute transporter Ostα/β, essential for bile acid ...Bile acid and steroid hormone homeostasis are critical for human health, with disruptions linked to metabolic and endocrine disorders. The organic solute transporter Ostα/β, essential for bile acid efflux in enterohepatic circulation, has long defied mechanistic elucidation. Here we present cryogenic electron microscopy structures of human Ostα/β in apo and substrate-bound states at 2.6-3.1 Å resolution, revealing a distinctive membrane protein architecture that defines a new transporter class. Ostα/β forms a symmetric tetramer of heterodimers, with each Ostα subunit showing a new seven-transmembrane fold, augmented by a single transmembrane helix of Ostβ. This architecture is stabilized by extensive lipid modifications, including a palmitoylated cysteine-rich motif that forms a lateral substrate-binding groove. The structures uncover a unique transport pathway featuring two substrate-binding sites connected by an amphipathic helix-gated conduit. This design, conserved in the evolutionarily related TMEM184 family, suggests an ancient mechanism for substrate translocation. Electrophysiological studies demonstrate voltage-sensitive, bidirectional transport driven by electrochemical gradients, elucidating the efflux role of Ostα/β in vivo. Lipid interactions, notably palmitoylation-dependent trafficking, emerge as critical for stability and function. These findings clarify the molecular mechanism of Ostα/β, provide a structural basis for disease-associated mutations and establish a paradigm for lipid-modified membrane transport.
History
DepositionApr 24, 2025-
Header (metadata) releaseDec 10, 2025-
Map releaseDec 10, 2025-
UpdateMar 18, 2026-
Current statusMar 18, 2026Processing site: PDBc / Status: Released

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Structure visualization

Supplemental images

emd_64369.png

Downloads & links

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Map

FileDownload / File: emd_64369.map.gz / Format: CCP4 / Size: 103 MB / Type: IMAGE STORED AS FLOATING POINT NUMBER (4 BYTES)
Projections & slices

Image control

Size
Brightness
Contrast
Others
AxesZ (Sec.)Y (Row.)X (Col.)
0.82 Å/pix.
x 300 pix.
= 247.2 Å		0.82 Å/pix.
x 300 pix.
= 247.2 Å		0.82 Å/pix.
x 300 pix.
= 247.2 Å

Surface

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Slices (1/3)

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Slices (2/3)

Images are generated by Spider.

Voxel sizeX=Y=Z: 0.824 Å
Density

Histogram

Histogram (log scale)
Contour LevelBy AUTHOR: 0.24
Minimum - Maximum-1.8434821 - 2.697545
Average (Standard dev.)0.00077664637 (±0.06909928)
SymmetrySpace group: 1
Details

EMDB XML:

Map geometry
Axis orderXYZ
Origin000
Dimensions300300300
Spacing300300300
CellA=B=C: 247.2 Å
α=β=γ: 90.0 °

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Supplemental data

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Mask #1

Fileemd_64369_msk_1.map
Projections & Slices
AxesZYX

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Half map: #2

Fileemd_64369_half_map_1.map
Projections & Slices
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Histogram

Histogram (log scale)

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Half map: #1

Fileemd_64369_half_map_2.map
Projections & Slices
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Sample components

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Entire : Heterodimer of Ost alpha and Ost beta

EntireName: Heterodimer of Ost alpha and Ost beta
Components
  • Complex: Heterodimer of Ost alpha and Ost beta
    • Protein or peptide: Organic solute transporter subunit alpha
    • Protein or peptide: Organic solute transporter subunit beta
  • Ligand: (7E,21R,24S)-27-amino-24-hydroxy-18,24-dioxo-19,23,25-trioxa-24lambda~5~-phosphaheptacos-7-en-21-yl (9Z,12E)-octadeca-9,12-dienoate
  • Ligand: PHOSPHATIDYL ETHANOL
  • Ligand: 1-O-OCTADECYL-SN-GLYCERO-3-PHOSPHOCHOLINE
  • Ligand: CHOLESTEROL
  • Ligand: PALMITIC ACID
  • Ligand: 17-oxoandrost-5-en-3beta-yl hydrogen sulfate
  • Ligand: water

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Supramolecule #1: Heterodimer of Ost alpha and Ost beta

SupramoleculeName: Heterodimer of Ost alpha and Ost beta / type: complex / ID: 1 / Parent: 0 / Macromolecule list: #1-#2
Source (natural)Organism: Homo sapiens (human)

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Macromolecule #1: Organic solute transporter subunit alpha

MacromoleculeName: Organic solute transporter subunit alpha / type: protein_or_peptide / ID: 1 / Number of copies: 2 / Enantiomer: LEVO
Source (natural)Organism: Homo sapiens (human)
Molecular weightTheoretical: 38.967082 KDa
Recombinant expressionOrganism: Homo sapiens (human)
SequenceString: MEPGRTQIKL DPRYTADLLE VLKTNYGIPS ACFSQPPTAA QLLRALGPVE LALTSILTLL ALGSIAIFLE DAVYLYKNTL CPIKRRTLL WKSSAPTVVS VLCCFGLWIP RSLVLVEMTI TSFYAVCFYL LMLVMVEGFG GKEAVLRTLR DTPMMVHTGP C CCCCPCCP ...String:
MEPGRTQIKL DPRYTADLLE VLKTNYGIPS ACFSQPPTAA QLLRALGPVE LALTSILTLL ALGSIAIFLE DAVYLYKNTL CPIKRRTLL WKSSAPTVVS VLCCFGLWIP RSLVLVEMTI TSFYAVCFYL LMLVMVEGFG GKEAVLRTLR DTPMMVHTGP C CCCCPCCP RLLLTRKKLQ LLMLGPFQYA FLKITLTLVG LFLVPDGIYD PADISEGSTA LWINTFLGVS TLLALWTLGI IS RQARLHL GEQNMGAKFA LFQVLLILTA LQPSIFSVLA NGGQIACSPP YSSKTRSQVM NCHLLILETF LMTVLTRMYY RRK DHKVGY ETFSSPDLDL NLKAGGSDYK DDDDK

UniProtKB: Organic solute transporter subunit alpha

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Macromolecule #2: Organic solute transporter subunit beta

MacromoleculeName: Organic solute transporter subunit beta / type: protein_or_peptide / ID: 2 / Number of copies: 2 / Enantiomer: LEVO
Source (natural)Organism: Homo sapiens (human)
Molecular weightTheoretical: 15.943913 KDa
Recombinant expressionOrganism: Homo sapiens (human)
SequenceString:
MEHSEGAPGD PAGTVVPQEL LEEMLWFFRV EDASPWNHSI LALAAVVVII SMVLLGRSIQ ASRKEKMQPP EKETPEVLHL DEAKDHNSL NNLRETLLSE KPNLAQVELE LKERDVLSVF LPDVPETESG GSHHHHHHHH HH

UniProtKB: Organic solute transporter subunit beta

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Macromolecule #3: (7E,21R,24S)-27-amino-24-hydroxy-18,24-dioxo-19,23,25-trioxa-24la...

MacromoleculeName: (7E,21R,24S)-27-amino-24-hydroxy-18,24-dioxo-19,23,25-trioxa-24lambda~5~-phosphaheptacos-7-en-21-yl (9Z,12E)-octadeca-9,12-dienoate
type: ligand / ID: 3 / Number of copies: 4 / Formula: 76F
Molecular weightTheoretical: 742.018 Da
Chemical component information

ChemComp-76F:
(7E,21R,24S)-27-amino-24-hydroxy-18,24-dioxo-19,23,25-trioxa-24lambda~5~-phosphaheptacos-7-en-21-yl (9Z,12E)-octadeca-9,12-dienoate

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Macromolecule #4: PHOSPHATIDYL ETHANOL

MacromoleculeName: PHOSPHATIDYL ETHANOL / type: ligand / ID: 4 / Number of copies: 2 / Formula: P0E
Molecular weightTheoretical: 716.965 Da
Chemical component information

ChemComp-P0E:
PHOSPHATIDYL ETHANOL

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Macromolecule #5: 1-O-OCTADECYL-SN-GLYCERO-3-PHOSPHOCHOLINE

MacromoleculeName: 1-O-OCTADECYL-SN-GLYCERO-3-PHOSPHOCHOLINE / type: ligand / ID: 5 / Number of copies: 2 / Formula: LPE
Molecular weightTheoretical: 510.708 Da
Chemical component information

ChemComp-LPE:
1-O-OCTADECYL-SN-GLYCERO-3-PHOSPHOCHOLINE

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Macromolecule #6: CHOLESTEROL

MacromoleculeName: CHOLESTEROL / type: ligand / ID: 6 / Number of copies: 32 / Formula: CLR
Molecular weightTheoretical: 386.654 Da
Chemical component information

ChemComp-CLR:
CHOLESTEROL

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Macromolecule #7: PALMITIC ACID

MacromoleculeName: PALMITIC ACID / type: ligand / ID: 7 / Number of copies: 12 / Formula: PLM
Molecular weightTheoretical: 256.424 Da
Chemical component information

ChemComp-PLM:
PALMITIC ACID

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Macromolecule #8: 17-oxoandrost-5-en-3beta-yl hydrogen sulfate

MacromoleculeName: 17-oxoandrost-5-en-3beta-yl hydrogen sulfate / type: ligand / ID: 8 / Number of copies: 4 / Formula: ZWY
Molecular weightTheoretical: 368.488 Da
Chemical component information

ChemComp-ZWY:
17-oxoandrost-5-en-3beta-yl hydrogen sulfate

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Macromolecule #9: water

MacromoleculeName: water / type: ligand / ID: 9 / Number of copies: 2 / Formula: HOH
Molecular weightTheoretical: 18.015 Da
Chemical component information

ChemComp-HOH:
WATER

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Experimental details

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Structure determination

Methodcryo EM
Processingsingle particle reconstruction
Aggregation stateparticle

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Sample preparation

BufferpH: 7.5
VitrificationCryogen name: ETHANE

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Electron microscopy

MicroscopeTFS KRIOS
Image recordingFilm or detector model: FEI FALCON IV (4k x 4k) / Average electron dose: 50.0 e/Å2
Electron beamAcceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
Electron opticsIllumination mode: SPOT SCAN / Imaging mode: DIFFRACTION / Nominal defocus max: 1.5 µm / Nominal defocus min: 1.0 µm
Experimental equipment
Model: Titan Krios / Image courtesy: FEI Company

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Image processing

CTF correctionType: NONE
Startup modelType of model: NONE
Final reconstructionResolution.type: BY AUTHOR / Resolution: 2.9 Å / Resolution method: FSC 0.143 CUT-OFF / Software - Name: cryoSPARC (ver. 4.6.2) / Software - details: Local refinement / Number images used: 81957
Initial angle assignmentType: MAXIMUM LIKELIHOOD
Final angle assignmentType: MAXIMUM LIKELIHOOD
FSC plot (resolution estimation)

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