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Azotobacter-vinelandii ferredoxin-i - alteration of individual surface-charges and the 4fe-4s (2+/+) cluster reduction potential

Academic Article
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Overview

authors

  • Shen, B. H.
  • Jollie, D. R.
  • Stout, C. David
  • Diller, T. C.
  • Armstrong, F. A.
  • Gorst, C. M.
  • Lamar, G. N.
  • Stephens, P. J.
  • Burgess, B. K.

publication date

  • March 1994

journal

  • Journal of Biological Chemistry  Journal

abstract

  • The structures of Azotobacter vinelandii ferredoxin I (AvFdI) and Peptococcus aerogenes ferredoxin (PaFd), near their analogous [4e-4S]2+/+ clusters, are highly conserved (Backes, G., Mino, Y., Loehr, T.M., Meyer, T.E., Cusanovich, M.A., Sweeney, W.V., Adman, E.T., and Sanders-Loehr, J. (1991) J. Am. Chem. Soc. 11, 2055-2064). Despite these similarities, the reduction potential (E0') of the AvFdI [4Fe-4S]2+/+ cluster is more than 200 mV more negative than that of PaFd. We have tested the contribution that individual amino acid residues make to the control of E0' by converting residues in AvFdI into the corresponding residue in PaFd. Four mutations involved substitutions of negatively charged surface residues with neutral residues and two involved substitution of buried hydrophobic residues. All AvFdI variants were characterized by x-ray crystallography, absorption, CD, EPR, and 1H NMR spectroscopies and by electrochemical methods. For the F25I mutation, significant structural changes occurred that affected the EPR and 1H NMR spectroscopic properties of AvFdI and had a minor influence on E0'. For all other mutations there were no changes in reduction potential. Thus we conclude, that variations in charged surface residues do not account for the observed differences in E0' between the analogous [4Fe-4S]2+/+ cluster of PaFd and AvFdI. These differences are therefore most likely to be due to differences in solvent accessibility.

subject areas

  • Amino Acid Sequence
  • Azotobacter vinelandii
  • Bacteria
  • Base Sequence
  • Circular Dichroism
  • Crystallography, X-Ray
  • Electron Spin Resonance Spectroscopy
  • Ferredoxins
  • Genes, Bacterial
  • Hydrogen Bonding
  • Iron
  • Magnetic Resonance Spectroscopy
  • Models, Molecular
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Oligodeoxyribonucleotides
  • Oxidation-Reduction
  • Potentiometry
  • Recombinant Proteins
  • Sequence Homology, Amino Acid
  • Spectrophotometry
  • Sulfur
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Identity

International Standard Serial Number (ISSN)

  • 0021-9258

PubMed ID

  • 8132582
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Additional Document Info

start page

  • 8564

end page

  • 8575

volume

  • 269

issue

  • 11

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