Skip to main content
PMC home page
Proceedings of the National Academy of Sciences of the United States of America logoLink to Proceedings of the National Academy of Sciences of the United States of America
. 1972 Dec;69(12):3526–3529. doi: 10.1073/pnas.69.12.3526

A Comparison of Fe4S4 Clusters in High-Potential Iron Protein and in Ferredoxin

C W Carter Jr †,‡, J Kraut †, S T Freer †, R A Alden †, L C Sieker §, E Adman §, L H Jensen §
PMCID: PMC389813  PMID: 4509310

Abstract

The structures of both oxidized (HPox) and reduced (HPred) high-potential iron protein and of oxidized ferredoxin (Fdox) have been partially refined at 2.0-Å resolution by methods similar to those applied to the protein rubredoxin [Watenpaugh, K. D., Sieker, L. C., Herriott, J. R. & Jensen, L. H. (1971) Cold Spring Harbor Symp. Quant. Biol. 36, 359-367]. Average bond lengths and angles in the HPred and Fdox Fe4S4* clusters are the same to within the root-mean square (rms) deviation of each mean value. A preliminary comparison of the two HiPIP oxidation states indicates that the HPox cluster is geometrically similar to the HPred cluster, but that it is smaller by 0.1-0.2 Å in certain dimensions. The HiPIP and ferredoxin cluster geometry is also nearly identical to that reported recently for a synthetic analog [Herskovitz, T., Averill, B. A., Holm, R. A., Ibers, J. A., Phillips, W. D. & Weither, J. F. (1972) Proc. Nat. Acad. Sci. USA 69, 2437-2441]. An apparent paradox presented by the large difference between the HiPIP and ferredoxin electrode potentials can be resolved by the assumption that the Fe4S4* cluster has not two but three oxidation states. The fully oxidized (HPox) and fully reduced (Fdred) clusters are paramagnetic, and the intermediate state is spin-paired [Tsibris, J. C. M. and Woody, R. W. (1970) Coord. Chem. Rev. 5, 417-458]. This hypothesis is supported by structural and spectroscopic evidence that the “paired-spin” state exists in both HPred and Fdox.

Keywords: protein structure refinement, electrode potentials

Full text

PDF
3526

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Carter C. W., Jr, Freer S. T., Xuong N. H., Alden R. A., Kraut J. Structure of the iron-sulfur cluster in the Chromatius iron protein at 2.25 Angstrom resolution. Cold Spring Harb Symp Quant Biol. 1972;36:381–385. doi: 10.1101/sqb.1972.036.01.049. [DOI] [PubMed] [Google Scholar]
  2. Hall D. O., Evans M. C. Iron-sulphur proteins. Nature. 1969 Sep 27;223(5213):1342–1348. doi: 10.1038/2231342a0. [DOI] [PubMed] [Google Scholar]
  3. Herskovitz T., Averill B. A., Holm R. H., Ibers J. A., Phillips W. D., Weiher J. F. Structure and properties of a synthetic analogue of bacterial iron--sulfur proteins. Proc Natl Acad Sci U S A. 1972 Sep;69(9):2437–2441. doi: 10.1073/pnas.69.9.2437. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Phillips W. D., Poe M., McDonald C. C., Bartsch R. G. Proton magnetic resonance studies of Chromatium high-potential iron protein. Proc Natl Acad Sci U S A. 1970 Oct;67(2):682–687. doi: 10.1073/pnas.67.2.682. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Poe M., Phillips W. D., McDonald C. C., Lovenberg W. Proton magnetic resonance study of ferredoxin from Clostridium pasteurianum. Proc Natl Acad Sci U S A. 1970 Apr;65(4):797–804. doi: 10.1073/pnas.65.4.797. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Sieker L. C., Adman E., Jensen L. H. Structure of the Fe-S complex in a bacterial ferredoxin. Nature. 1972 Jan 7;235(5332):40–42. doi: 10.1038/235040a0. [DOI] [PubMed] [Google Scholar]
  7. Strahs G., Kraut J. Low-resolution electron-density and anomalous-scattering-density maps of Chromatium high-potential iron protein. J Mol Biol. 1968 Aug 14;35(3):503–512. doi: 10.1016/s0022-2836(68)80010-5. [DOI] [PubMed] [Google Scholar]
  8. Watenpaugh K. D., Sieker L. C., Herriott J. R., Jensen L. H. The structure of a non-heme iron protein: rubredoxin at 1.5 Angstrom resolution. Cold Spring Harb Symp Quant Biol. 1972;36:359–367. doi: 10.1101/sqb.1972.036.01.047. [DOI] [PubMed] [Google Scholar]

Articles from Proceedings of the National Academy of Sciences of the United States of America are provided here courtesy of National Academy of Sciences

RESOURCES