E.coli IscA crystal structure to 2.3 A

Experimental Data Snapshot

  • Resolution: 2.30 Å
  • R-Value Free: 0.250 
  • R-Value Work: 0.212 
  • R-Value Observed: 0.215 

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Crystal structure of IscA, an iron-sulfur cluster assembly protein from Escherichia coli.

Cupp-Vickery, J.R.Silberg, J.J.Ta, D.T.Vickery, L.E.

(2004) J Mol Biol 338: 127-137

  • DOI: https://doi.org/10.1016/j.jmb.2004.02.027
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    IscA, an 11 kDa member of the hesB family of proteins, binds iron and [2Fe-2S] clusters, and participates in the biosynthesis of iron-sulfur proteins. We report the crystal structure of the apo-protein form of IscA from Escherichia coli to a resolution of 2.3A. The crystals belong to the space group P3(2)21 and have unit cell dimensions a=b=66.104 A, c=150.167 A (alpha=beta=90 degrees, gamma=120 degrees ). The structure was solved using single-wavelength anomalous dispersion (SAD) phasing of a selenomethionyl derivative, and the IscA model was refined to R=21.4% (Rfree=25.4%). IscA exists as an (alpha1alpha2)2 homotetramer with the (alpha1alpha2) dimer comprising the asymmetric unit. Cys35, implicated in Fe-S cluster assembly, is located in a central cavity formed at the tetramer interface with the gamma-sulfur atoms of residues from the alpha1 and alpha2' monomers (and alpha1'alpha2) positioned close to one another (approximately equal 7 A). C-terminal residues 99-107 are disordered, and the exact positions of Cys99 and Cys101 could not be determined. However, computer modeling of C-terminal residues in the tetramer suggests that Cys99 and Cys101 in the alpha1 monomer and those of the alpha1' monomer (or alpha2 and alpha2') are positioned sufficiently close to coordinate [2Fe-2S] clusters between the two dimers, whereas this is not possible within the (alpha1alpha2) or (alpha1'alpha2') dimer. This symmetrical arrangement allows for binding of two [2Fe-2S] clusters on opposite sides of the tetramer. Modeling further reveals that Cys101 is positioned sufficiently close to Cys35 to allow Cys35 to participate in cluster assembly, formation, or transfer.

  • Organizational Affiliation

    Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA. jvickery@uci.edu

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Protein yfhF
A, B
107Escherichia coliMutation(s): 1 
Gene Names: YFHFB2528C3053Z3795ECS3394SF2575S2747
Find proteins for P0AAC8 (Escherichia coli (strain K12))
Explore P0AAC8 
Go to UniProtKB:  P0AAC8
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP0AAC8
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.30 Å
  • R-Value Free: 0.250 
  • R-Value Work: 0.212 
  • R-Value Observed: 0.215 
  • Space Group: P 32 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 66.252α = 90
b = 66.252β = 90
c = 150.85γ = 120
Software Package:
Software NamePurpose
MOSFLMdata reduction
CCP4data scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2004-06-01
    Type: Initial release
  • Version 1.1: 2008-04-29
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2018-01-31
    Changes: Experimental preparation
  • Version 1.4: 2021-10-27
    Changes: Database references
  • Version 1.5: 2024-02-14
    Changes: Data collection