5GU7

Crystal Structure of human ERp44 form II


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.05 Å
  • R-Value Free: 0.235 
  • R-Value Work: 0.200 
  • R-Value Observed: 0.202 

Starting Model: experimental
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This is version 1.2 of the entry. See complete history


Literature

Structural basis of pH-dependent client binding by ERp44, a key regulator of protein secretion at the ER-Golgi interface

Watanabe, S.Harayama, M.Kanemura, S.Sitia, R.Inaba, K.

(2017) Proc Natl Acad Sci U S A 114: E3224-E3232

  • DOI: https://doi.org/10.1073/pnas.1621426114
  • Primary Citation of Related Structures:  
    5GU6, 5GU7

  • PubMed Abstract: 

    ERp44 retrieves some endoplasmic reticulum (ER)-resident enzymes and immature oligomers of secretory proteins from the Golgi. Association of ERp44 with its clients is regulated by pH-dependent mechanisms, but the molecular details are not fully understood. Here we report high-resolution crystal structures of human ERp44 at neutral and weakly acidic pH. These structures reveal key regions in the C-terminal tail (C tail) missing in the original crystal structure, including a regulatory histidine-rich region and a subsequent extended loop. The former region forms a short α-helix (α16), generating a histidine-clustered site (His cluster). At low pH, the three Trx-like domains of ERp44 ("a," "b," and "b'") undergo significant rearrangements, likely induced by protonation of His157 located at the interface between the a and b domains. The α16-helix is partially unwound and the extended loop is disordered in weakly acidic conditions, probably due to electrostatic repulsion between the protonated histidines in the His cluster. Molecular dynamics simulations indicated that helix unwinding enhances the flexibility of the C tail, disrupting its normal hydrogen-bonding pattern. The observed pH-dependent conformational changes significantly enlarge the positively charged regions around the client-binding site of ERp44 at low pH. Mutational analyses showed that ERp44 forms mixed disulfides with specific cysteines residing on negatively charged loop regions of Ero1α. We propose that the protonation states of the essential histidines regulate the ERp44-client interaction by altering the C-tail dynamics and surface electrostatic potential of ERp44.


  • Organizational Affiliation

    Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan.


Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Endoplasmic reticulum resident protein 44A [auth C]396Homo sapiensMutation(s): 0 
Gene Names: ERP44KIAA0573TXNDC4UNQ532/PRO1075
UniProt & NIH Common Fund Data Resources
Find proteins for Q9BS26 (Homo sapiens)
Explore Q9BS26 
Go to UniProtKB:  Q9BS26
PHAROS:  Q9BS26
GTEx:  ENSG00000023318 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ9BS26
Sequence Annotations
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.05 Å
  • R-Value Free: 0.235 
  • R-Value Work: 0.200 
  • R-Value Observed: 0.202 
  • Space Group: P 31 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 84.15α = 90
b = 84.15β = 90
c = 133.18γ = 120
Software Package:
Software NamePurpose
XDSdata reduction
XSCALEdata scaling
MOLREPphasing
Cootmodel building
PHENIXrefinement

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2017-04-12
    Type: Initial release
  • Version 1.1: 2017-05-03
    Changes: Database references
  • Version 1.2: 2023-11-08
    Changes: Data collection, Database references, Refinement description