Antisymmetric exchange in [2Fe-2S]1+ clusters: EPR of the Rieske protein from Thermus thermophilus at pH 14.

TitleAntisymmetric exchange in [2Fe-2S]1+ clusters: EPR of the Rieske protein from Thermus thermophilus at pH 14.
Publication TypeJournal Article
Year of Publication2004
Authorsde Oliveira, FTiago, Bominaar, EL, Hirst, J, Fee, JA, Münck, E
JournalJ Am Chem Soc
Volume126
Issue17
Pagination5338-9
Date Published2004 May 05
ISSN0002-7863
KeywordsElectron Spin Resonance Spectroscopy, Electron Transport Complex III, Hydrogen-Ion Concentration, Iron, Iron-Sulfur Proteins, Sulfur, Thermus thermophilus
Abstract

[2Fe-2S] clusters found in the xanthine oxidase family of proteins exhibit an S = 1/2 EPR feature, called signal II, for which one g-value is significantly above g = 2.0. The g-values of signal II cannot be explained with the standard spin coupling model that has been so successful in describing the g = 1.94 signals of [2Fe-2S] ferredoxins. We have studied the EPR spectra of the Rieske protein from Thermus thermophilus at pH 14 and observed a signal II-type EPR spectrum, with g-values at 1.81, 1.94, and 2.14. It is shown that the g-values of signal II can be explained by including an antisymmetric exchange term, d.S1xS2, in the spin Hamiltonian. The presence of this term is sensed by EPR if the isotropic exchange coupling constant J is sufficiently small. For the Rieske protein we determined J = 43 cm-1 which is at least 4 times smaller than the J values reported for [2Fe-2S] clusters that yield standard g = 1.94 signals.

DOI10.1021/ja031746a
Alternate JournalJ. Am. Chem. Soc.
Citation Key10.1021/ja031746a
PubMed ID15113187
Grant ListGM35342 / GM / NIGMS NIH HHS / United States