ISC-like [2Fe-2S] ferredoxin (FdxB) dimer from Pseudomonas putida JCM 20004: structural and electron-nuclear double resonance characterization

J Biol Inorg Chem. 2011 Aug;16(6):923-35. doi: 10.1007/s00775-011-0793-8. Epub 2011 Jun 7.


The crystal structure of the ISC-like [2Fe-2S] ferredoxin (FdxB), probably involved in the de novo iron-sulfur cluster biosynthesis (ISC) system of Pseudomonas putida JCM 20004, was determined at 1.90-Å resolution and displayed a novel tail-to-tail dimeric form. P. putida FdxB lacks the consensus free cysteine usually present near the cluster of ISC-like ferredoxins, indicating its primarily electron transfer role in the iron-sulfur cluster. Orientation-selective electron-nuclear double resonance spectroscopic analysis of reduced FdxB in conjunction with the crystal structure has identified the innermost Fe2 site with a high positive spin population as the nonreducible iron retaining the Fe(3+) valence and the outermost Fe1 site as the reduced iron with a low negative spin density. The average g (max) direction is skewed, forming an angle of about 27.3° (±4°) with the normal of the [2Fe-2S] plane, whereas the g (int) and g (min) directions are distributed in the cluster plane, presumably tilted by the same angle with respect to this plane. These results are related to those for other [2Fe-2S] proteins in different electron transport chains (e.g. adrenodoxin) and suggest a significant distortion of the electronic structure of the reduced [2Fe-2S] cluster under the influence of the protein environment around each iron site in general.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / metabolism
  • Crystallography, X-Ray
  • Electron Spin Resonance Spectroscopy / methods*
  • Ferredoxins / chemistry*
  • Ferredoxins / metabolism
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Conformation
  • Protein Multimerization
  • Pseudomonas putida / chemistry
  • Pseudomonas putida / metabolism*
  • Sequence Alignment


  • 2Fe-2S ferredoxin
  • Bacterial Proteins
  • Ferredoxins

Associated data

  • PDB/3AH7