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- EMDB-66144: cryo-EM structure of human organic solute transporter in apo state -

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Basic information

Entry
Database: EMDB / ID: EMD-66144
Titlecryo-EM structure of human organic solute transporter in apo state
Map data
Sample
  • Complex: cryo-EM structure of human organic solute transporter in apo state
    • Protein or peptide: Organic solute transporter subunit alpha
    • Protein or peptide: Organic solute transporter subunit beta
  • Ligand: CHOLESTEROL
  • Ligand: PALMITIC ACID
  • Ligand: (2S)-3-(hexadecanoyloxy)-2-[(9Z)-octadec-9-enoyloxy]propyl 2-(trimethylammonio)ethyl phosphate
Keywordsapo / TRANSPORTER / TRANSPORT PROTEIN
Function / homology
Function and homology information


bile acid secretion / bile acid transmembrane transporter activity / Recycling of bile acids and salts / bile acid and bile salt transport / transmembrane transporter activity / basolateral plasma membrane / protein heterodimerization activity / endoplasmic reticulum membrane / protein homodimerization activity / protein-containing complex ...bile acid secretion / bile acid transmembrane transporter activity / Recycling of bile acids and salts / bile acid and bile salt transport / transmembrane transporter activity / 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: 2.81 Å
AuthorsSun X / Yao D / Xue J
Funding support China, 1 items
OrganizationGrant numberCountry
National Natural Science Foundation of China (NSFC)NCTIB2022HS02004 China
CitationJournal: Nat Struct Mol Biol / Year: 2026
Title: Structural insights into OSTα/β-mediated transport of bile acids and steroid conjugates.
Authors: Xicheng Sun / Taikun Tian / Minying Low / Shaobai Li / Deqiang Yao / Yanmei Yuan / Mi Cao / Ming Lei / Yong Wang / Hongwen Chen / Pengfei Lan / Qiang Xia / Jing Xue /
Abstract: Mammalian organic solute transporter α/β (OSTα/β) is crucial for the enterohepatic circulation of bile acids and the homeostasis of steroid conjugates, mediating their movement across membranes ...Mammalian organic solute transporter α/β (OSTα/β) is crucial for the enterohepatic circulation of bile acids and the homeostasis of steroid conjugates, mediating their movement across membranes as an obligate heterodimer. Here we present high-resolution cryo-EM structures of human OSTα/β in apo, substrate-bound and inhibitor-bound states, revealing a tetrameric organization as a homodimer of heterodimers that is required for membrane activity. Substrates bind within a surface-exposed tunnel formed by transmembrane helices 5 and 6, which is unexpectedly sealed by multiple palmitoyl chains covalently attached to a conserved intracellular loop IL2. Two chemically distinct inhibitors, fidaxomicin and ethinylestradiol, disrupt transport by both competing for the substrate-binding pocket and sterically occluding the tunnel. Together with biochemical and evolutionary analyses, our work defines a distinctive class of solute carriers that uses palmitoylation to facilitate substrate transport, a mechanism conserved across eukaryotes.
History
DepositionSep 9, 2025-
Header (metadata) releaseJun 10, 2026-
Map releaseJun 10, 2026-
UpdateOct 7, 2026-
Current statusOct 7, 2026Processing site: PDBc / Status: Released

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Structure visualization

Supplemental images

emd_66144.png

Downloads & links

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Map

FileDownload / File: emd_66144.map.gz / Format: CCP4 / Size: 30.5 MB / Type: IMAGE STORED AS FLOATING POINT NUMBER (4 BYTES)
Projections & slices

Image control

Size
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AxesZ (Sec.)Y (Row.)X (Col.)
1.1 Å/pix.
x 200 pix.
= 220. Å		1.1 Å/pix.
x 200 pix.
= 220. Å		1.1 Å/pix.
x 200 pix.
= 220. Å

Surface

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Images are generated by Spider.

Voxel sizeX=Y=Z: 1.1 Å
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Histogram

Histogram (log scale)
Contour LevelBy AUTHOR: 0.3
Minimum - Maximum-2.216426 - 2.9838006
Average (Standard dev.)-0.00019921713 (±0.079912)
SymmetrySpace group: 1
Details

EMDB XML:

Map geometry
Axis orderXYZ
Origin000
Dimensions200200200
Spacing200200200
CellA=B=C: 220.0 Å
α=β=γ: 90.0 °

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Supplemental data

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Half map: #2

Fileemd_66144_half_map_1.map
Projections & Slices
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Histogram

Histogram (log scale)

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Half map: #1

Fileemd_66144_half_map_2.map
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Sample components

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Entire : cryo-EM structure of human organic solute transporter in apo state

EntireName: cryo-EM structure of human organic solute transporter in apo state
Components
  • Complex: cryo-EM structure of human organic solute transporter in apo state
    • Protein or peptide: Organic solute transporter subunit alpha
    • Protein or peptide: Organic solute transporter subunit beta
  • Ligand: CHOLESTEROL
  • Ligand: PALMITIC ACID
  • Ligand: (2S)-3-(hexadecanoyloxy)-2-[(9Z)-octadec-9-enoyloxy]propyl 2-(trimethylammonio)ethyl phosphate

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Supramolecule #1: cryo-EM structure of human organic solute transporter in apo state

SupramoleculeName: cryo-EM structure of human organic solute transporter in apo state
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: 37.768938 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 NLKA

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: 14.361263 KDa
Recombinant expressionOrganism: Homo sapiens (human)
SequenceString:
MEHSEGAPGD PAGTVVPQEL LEEMLWFFRV EDASPWNHSI LALAAVVVII SMVLLGRSIQ ASRKEKMQPP EKETPEVLHL DEAKDHNSL NNLRETLLSE KPNLAQVELE LKERDVLSVF LPDVPETES

UniProtKB: Organic solute transporter subunit beta

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Macromolecule #3: CHOLESTEROL

MacromoleculeName: CHOLESTEROL / type: ligand / ID: 3 / Number of copies: 10 / Formula: CLR
Molecular weightTheoretical: 386.654 Da
Chemical component information

ChemComp-CLR:
CHOLESTEROL

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Macromolecule #4: PALMITIC ACID

MacromoleculeName: PALMITIC ACID / type: ligand / ID: 4 / Number of copies: 14 / Formula: PLM
Molecular weightTheoretical: 256.424 Da
Chemical component information

ChemComp-PLM:
PALMITIC ACID

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Macromolecule #5: (2S)-3-(hexadecanoyloxy)-2-[(9Z)-octadec-9-enoyloxy]propyl 2-(tri...

MacromoleculeName: (2S)-3-(hexadecanoyloxy)-2-[(9Z)-octadec-9-enoyloxy]propyl 2-(trimethylammonio)ethyl phosphate
type: ligand / ID: 5 / Number of copies: 6 / Formula: POV
Molecular weightTheoretical: 760.076 Da
Chemical component information

ChemComp-POV:
(2S)-3-(hexadecanoyloxy)-2-[(9Z)-octadec-9-enoyloxy]propyl 2-(trimethylammonio)ethyl phosphate / phospholipid*YM

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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

MicroscopeFEI/PHILIPS CM300FEG/T
Image recordingFilm or detector model: GATAN K3 (6k x 4k) / Average electron dose: 50.0 e/Å2
Electron beamAcceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
Electron opticsIllumination mode: FLOOD BEAM / Imaging mode: BRIGHT FIELD / Nominal defocus max: 1.7 µm / Nominal defocus min: 0.9 µm

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Image processing

CTF correctionType: PHASE FLIPPING AND AMPLITUDE CORRECTION
Startup modelType of model: OTHER
Final reconstructionResolution.type: BY AUTHOR / Resolution: 2.81 Å / Resolution method: FSC 0.143 CUT-OFF / Software - Name: cryoSPARC / Number images used: 799885
Initial angle assignmentType: RANDOM ASSIGNMENT
Final angle assignmentType: MAXIMUM LIKELIHOOD
FSC plot (resolution estimation)

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