2VQ3

Crystal Structure of the Membrane Proximal Oxidoreductase Domain of Human Steap3, the Dominant Ferric Reductase of the Erythroid Transferrin Cycle


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.00 Å
  • R-Value Free: 0.236 
  • R-Value Work: 0.197 
  • R-Value Observed: 0.199 

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This is version 1.4 of the entry. See complete history


Literature

Structure of the Membrane Proximal Oxidoreductase Domain of Human Steap3, the Dominant Ferrireductase of the Erythroid Transferrin Cycle

Sendamarai, A.K.Ohgami, R.S.Fleming, M.D.Lawrence, C.M.

(2008) Proc Natl Acad Sci U S A 105: 7410

  • DOI: https://doi.org/10.1073/pnas.0801318105
  • Primary Citation of Related Structures:  
    2VNS, 2VQ3

  • PubMed Abstract: 

    The daily production of 200 billion erythrocytes requires 20 mg of iron, accounting for nearly 80% of the iron demand in humans. Thus, erythroid precursor cells possess an efficient mechanism for iron uptake in which iron loaded transferrin (Tf) binds to the transferrin receptor (TfR) at the cell surface. The Tf:TfR complex then enters the endosome via receptor-mediated endocytosis. Upon endosomal acidification, iron is released from Tf, reduced to Fe(2+) by Steap3, and transported across the endosomal membrane by divalent metal iron transporter 1. Steap3, the major ferrireductase in erythrocyte endosomes, is a member of a unique family of reductases. Steap3 is comprised of an N-terminal cytosolic oxidoreductase domain and a C-terminal heme-containing transmembrane domain. Cytosolic NADPH and a flavin are predicted cofactors, but the NADPH/flavin binding domain differs significantly from those in other eukaryotic reductases. Instead, Steap3 shows remarkable, although limited homology to FNO, an archaeal oxidoreductase. We have determined the crystal structure of the human Steap3 oxidoreductase domain in the absence and presence of NADPH. The structure reveals an FNO-like domain with an unexpected dimer interface and substrate binding sites that are well positioned to direct electron transfer from the cytosol to a heme moiety predicted to be fixed within the transmembrane domain. Here, we discuss possible gating mechanisms for electron transfer across the endosomal membrane.


  • Organizational Affiliation

    Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA.


Macromolecules
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Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
METALLOREDUCTASE STEAP3
A, B
215Homo sapiensMutation(s): 0 
EC: 1.16.1.2 (PDB Primary Data), 1.16.1 (PDB Primary Data)
UniProt & NIH Common Fund Data Resources
Find proteins for Q658P3 (Homo sapiens)
Explore Q658P3 
Go to UniProtKB:  Q658P3
PHAROS:  Q658P3
GTEx:  ENSG00000115107 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ658P3
Sequence Annotations
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.00 Å
  • R-Value Free: 0.236 
  • R-Value Work: 0.197 
  • R-Value Observed: 0.199 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 37.686α = 90
b = 66.812β = 90
c = 143.366γ = 90
Software Package:
Software NamePurpose
REFMACrefinement
HKLdata reduction
SCALEPACKdata scaling
REFMACphasing

Structure Validation

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Ligand Structure Quality Assessment 


Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2008-05-06
    Type: Initial release
  • Version 1.1: 2011-05-08
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2022-11-02
    Changes: Database references, Other
  • Version 1.4: 2024-01-31
    Changes: Data collection, Refinement description