7NIU

Nanodisc reconstituted human ABCB4 in complex with 4B1-Fab and QA2-Fab (apo-inward-open conformation)


Experimental Data Snapshot

  • Method: ELECTRON MICROSCOPY
  • Resolution: 4.20 Å
  • Aggregation State: PARTICLE 
  • Reconstruction Method: SINGLE PARTICLE 

wwPDB Validation   3D Report Full Report


This is version 1.1 of the entry. See complete history


Literature

Structures of ABCB4 provide insight into phosphatidylcholine translocation.

Nosol, K.Bang-Sorensen, R.Irobalieva, R.N.Erramilli, S.K.Stieger, B.Kossiakoff, A.A.Locher, K.P.

(2021) Proc Natl Acad Sci U S A 118

  • DOI: https://doi.org/10.1073/pnas.2106702118
  • Primary Citation of Related Structures:  
    7NIU, 7NIV, 7NIW

  • PubMed Abstract: 

    ABCB4 is expressed in hepatocytes and translocates phosphatidylcholine into bile canaliculi. The mechanism of specific lipid recruitment from the canalicular membrane, which is essential to mitigate the cytotoxicity of bile salts, is poorly understood. We present cryogenic electron microscopy structures of human ABCB4 in three distinct functional conformations. An apo-inward structure reveals how phospholipid can be recruited from the inner leaflet of the membrane without flipping its orientation. An occluded structure reveals a single phospholipid molecule in a central cavity. Its choline moiety is stabilized by cation-π interactions with an essential tryptophan residue, rationalizing the specificity of ABCB4 for phosphatidylcholine. In an inhibitor-bound structure, a posaconazole molecule blocks phospholipids from reaching the central cavity. Using a proteoliposome-based translocation assay with fluorescently labeled phosphatidylcholine analogs, we recapitulated the substrate specificity of ABCB4 in vitro and confirmed the role of the key tryptophan residue. Our results provide a structural basis for understanding an essential translocation step in the generation of bile and its sensitivity to azole drugs.


  • Organizational Affiliation

    Institute of Molecular Biology and Biophysics, ETH Zürich, 8093 Zürich, Switzerland.


Macromolecules
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Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Isoform 2 of Phosphatidylcholine translocator ABCB41,279Homo sapiensMutation(s): 0 
Gene Names: ABCB4MDR3PGY3
EC: 7.6.2.1
Membrane Entity: Yes 
UniProt & NIH Common Fund Data Resources
Find proteins for P21439 (Homo sapiens)
Explore P21439 
Go to UniProtKB:  P21439
PHAROS:  P21439
GTEx:  ENSG00000005471 
Entity Groups  
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UniProt GroupP21439
Sequence Annotations
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  • Reference Sequence
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Entity ID: 2
MoleculeChains Sequence LengthOrganismDetailsImage
QA2 Fab-fragment light chainB [auth D]215Homo sapiensMutation(s): 0 
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Entity ID: 3
MoleculeChains Sequence LengthOrganismDetailsImage
QA2 Fab-fragment heavy chainC [auth E]234Homo sapiensMutation(s): 0 
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Entity ID: 4
MoleculeChains Sequence LengthOrganismDetailsImage
4B1 Fab-fragment light chainD [auth B]215Homo sapiensMutation(s): 0 
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Entity ID: 5
MoleculeChains Sequence LengthOrganismDetailsImage
4B1 Fab-fragment heavy chainE [auth C]241Homo sapiensMutation(s): 0 
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: ELECTRON MICROSCOPY
  • Resolution: 4.20 Å
  • Aggregation State: PARTICLE 
  • Reconstruction Method: SINGLE PARTICLE 

Structure Validation

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Entry History & Funding Information

Deposition Data


Funding OrganizationLocationGrant Number
Swiss National Science FoundationSwitzerland310030_189111
Swiss National Science FoundationSwitzerland310030_155563
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)United StatesGM117372

Revision History  (Full details and data files)

  • Version 1.0: 2021-08-25
    Type: Initial release
  • Version 1.1: 2024-11-13
    Changes: Data collection, Structure summary