X-ray crystal structure of E. coli IscS

Experimental Data Snapshot

  • Resolution: 2.10 Å
  • R-Value Free: 0.236 
  • R-Value Work: 0.206 
  • R-Value Observed: 0.206 

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Crystal Structure of IscS, a Cysteine Desulfurase from Escherichia coli

Cupp-Vickery, J.R.Urbina, H.Vickery, L.E.

(2003) J Mol Biol 330: 1049-1059

  • DOI: https://doi.org/10.1016/s0022-2836(03)00690-9
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    IscS is a widely distributed cysteine desulfurase that catalyzes the pyridoxal phosphate-dependent desulfuration of L-cysteine and plays a central role in the delivery of sulfur to a variety of metabolic pathways. We report the crystal structure of Escherichia coli IscS to a resolution of 2.1A. The crystals belong to the space group P2(1)2(1)2(1) and have unit cell dimensions a=73.70A, b=101.97A, c=108.62A (alpha=beta=gamma=90 degrees ). Molecular replacement with the Thermotoga maritima NifS model was used to determine phasing, and the IscS model was refined to an R=20.6% (R(free)=23.6%) with two molecules per asymmetric unit. The structure of E.coli IscS is similar to that of T.maritima NifS with nearly identical secondary structure and an overall backbone r.m.s. difference of 1.4A. However, in contrast to NifS a peptide segment containing the catalytic cysteine residue (Cys328) is partially ordered in the IscS structure. This segment of IscS (residues 323-335) forms a surface loop directed away from the active site pocket. Cys328 is positioned greater than 17A from the pyridoxal phosphate cofactor, suggesting that a large conformational change must occur during catalysis in order for Cys328 to participate in nucleophilic attack of a pyridoxal phosphate-bound cysteine substrate. Modeling suggests that rotation of this loop may allow movement of Cys328 to within approximately 3A of the pyridoxal phosphate cofactor.

  • Organizational Affiliation

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

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Cysteine desulfuraseA [auth B],
B [auth A]
404Escherichia coliMutation(s): 0 
Gene Names: ISCS OR B2530 OR C3056 OR Z3797 OR ECS3396 OR SF2577
EC: 4.4.1
Find proteins for P0A6B7 (Escherichia coli (strain K12))
Explore P0A6B7 
Go to UniProtKB:  P0A6B7
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP0A6B7
Sequence Annotations
  • Reference Sequence
Small Molecules
Experimental Data & Validation

Experimental Data

  • Resolution: 2.10 Å
  • R-Value Free: 0.236 
  • R-Value Work: 0.206 
  • R-Value Observed: 0.206 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 73.709α = 90
b = 101.974β = 90
c = 108.617γ = 90
Software Package:
Software NamePurpose
MOSFLMdata reduction
SCALAdata scaling
CCP4data scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2003-07-22
    Type: Initial release
  • Version 1.1: 2008-04-29
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Non-polymer description, Version format compliance
  • Version 1.3: 2018-01-31
    Changes: Experimental preparation
  • Version 1.4: 2024-04-03
    Changes: Data collection, Database references, Derived calculations, Refinement description