Two crystal structures of the cytoplasmic molybdate-binding protein ModG suggest a novel cooperative binding mechanism and provide insights into ligand-binding specificity. Phosphate-grown form with molybdate and phosphate bound

Experimental Data Snapshot

  • Resolution: 1.80 Å
  • R-Value Free: 0.266 
  • R-Value Work: 0.200 

wwPDB Validation   3D Report Full Report

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Two Crystal Structures of the Cytoplasmic Molybdate-Binding Protein Modg Suggest a Novel Cooperative Binding Mechanism and Provide Insights Into Ligand-Binding Specificity

Delarbre, L.Stevenson, C.E.M.White, D.J.Mitchenall, L.A.Pau, R.N.Lawson, D.M.

(2001) J Mol Biol 308: 1063

  • DOI: https://doi.org/10.1006/jmbi.2001.4636
  • Primary Citation of Related Structures:  
    1H9J, 1H9K, 1H9M

  • PubMed Abstract: 

    The X-ray structures of the cytoplasmic molybdate-binding protein ModG from Azotobacter vinelandii in two different crystal forms have been determined. For such a small protein it is remarkably complex. Each 14.3 kDa subunit contains two small beta-barrel domains, which display an OB-fold motif, also seen in the related structure of ModE, a molybdenum-dependent transcriptional regulator, and very recently in the Mop protein that, like ModG, has been implicated in molybdenum homeostasis within the cell. In contrast to earlier speculation, the functional unit of ModG is actually not a dimer (as in ModE), but a trimer capable of binding a total of eight molybdate molecules that are distributed between two disparate types of site. All the binding sites are located at subunit interfaces, with one type lying on a crystallographic 3-fold axis, whilst the other lies between pairs of subunits. The two types of site are linked by short hydrogen bond networks that may suggest a cooperative binding mechanism. A superposition of two subunits of the ModG trimer on the apo-ModE dimer allows the probable locations of the molybdate-binding sites of the latter to be assigned. Through structural comparisons with other oxyanion-binding proteins, including Mop and ModE, it is possible to speculate about ligand-binding affinities, selectivity and evolution.

  • Organizational Affiliation

    Department of Biological Chemistry, Norwich, NR4 7UH, UK.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
MOLYBDENUM-BINDING-PROTEIN145Azotobacter vinelandiiMutation(s): 0 
Gene Names: MODG
Find proteins for Q44529 (Azotobacter vinelandii)
Explore Q44529 
Go to UniProtKB:  Q44529
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ44529
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.80 Å
  • R-Value Free: 0.266 
  • R-Value Work: 0.200 
  • Space Group: P 3 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 50.685α = 90
b = 50.685β = 90
c = 79.112γ = 120
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2001-05-11
    Type: Initial release
  • Version 1.1: 2011-05-07
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2019-03-06
    Changes: Data collection, Experimental preparation, Other
  • Version 1.4: 2024-05-08
    Changes: Data collection, Database references, Other