Issue 31, 2009
From the journal:

Physical Chemistry Chemical Physics

The reduced [2Fe-2S] clusters in adrenodoxin and Arthrospira platensisferredoxin share spin density with proteinnitrogens, probed using 2D ESEEM†

Sergei A. Dikanov,*a   Rimma I. Samoilova,b   Reinhard Kappl,c   Antony R. Croftsd  and  Jürgen Hüttermannc  

* Corresponding authors

a Department of Veterinary Clinical Medicine, University of Illinois, Urbana, USA
E-mail: dikanov@illinois.edu

b Institute of Chemical Kinetics and Combustion, Russian Academy of Sciences, Novosibirsk 630090, Russia

c Fachrichtung Biophysik, Universität des Saarlandes, 66421 Homburg/Saar, Germany

d Department of Biochemistry, University of Illinois, Urbana, USA

Abstract

We have used X-band ESEEM to study the reduced [2Fe-2S] cluster in adrenodoxin and Arthrospira platensisferredoxin. By use of a 2D approach (HYSCORE), we have shown that the cluster is involved in weak magnetic interactions with several nitrogens in each protein. Despite substantial differences in the shape and orientational dependence of individual cross-peaks, the major spectral features in both proteins are attributable to two peptide nitrogens (N1 and N2) with similar hyperfine couplings ∼1.1 and ∼0.70 MHz. The couplings determined represent a small fraction (0.0003–0.0005) of the unpaired spin density of the reduced cluster transferred to these nitrogens over H-bond bridges or the covalent bonds of cysteine ligands. Simulation of the HYSCORE spectra has allowed us to estimate the orientation of the nuclear quadrupole tensors of N1 and N2 in the g-tensor coordinate system. The most likely candidates for the role of N1 and N2 have been identified in the protein environment by comparing magnetic-resonance data with crystallographic structures of the oxidized proteins. A possible influence of redox-linked structural changes on ESEEM data is analyzed using available structures for related proteins in two redox states.

Graphical abstract: The reduced [2Fe-2S] clusters in adrenodoxin and Arthrospira platensisferredoxin share spin density with protein nitrogens, probed using 2D ESEEM

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Article information

DOI
https://doi.org/10.1039/B904597J
Article type
Paper
Submitted
05 Mar 2009
Accepted
11 Jun 2009
First published
01 Jul 2009

Phys. Chem. Chem. Phys., 2009,11, 6807-6819

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The reduced [2Fe-2S] clusters in adrenodoxin and Arthrospira platensisferredoxin share spin density with protein nitrogens, probed using 2D ESEEM

S. A. Dikanov, R. I. Samoilova, R. Kappl, A. R. Crofts and J. Hüttermann, Phys. Chem. Chem. Phys., 2009, 11, 6807 DOI: 10.1039/B904597J

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