Spectroscopic and redox studies of valence-delocalized [Fe2S2](+) centers in thioredoxin-like ferredoxins

Journal of the American Chemical Society
Sowmya SubramanianM K Johnson

Abstract

Reduced forms of the C56S and C60S variants of the thioredoxin-like Clostridium pasteurianum [Fe2S2] ferredoxin (CpFd) provide the only known examples of valence-delocalized [Fe2S2](+) clusters, which constitute a fundamental building block of all higher nuclearity Fe-S clusters. In this work, we have revisited earlier work on the CpFd variants and carried out redox and spectroscopic studies on the [Fe2S2](2+,+) centers in wild-type and equivalent variants of the highly homologous and structurally characterized Aquifex aeolicus ferredoxin 4 (AaeFd4) using EPR, UV-visible-NIR absorption, CD and variable-temperature MCD, and protein-film electrochemistry. The results indicate that the [Fe2S2](+) centers in the equivalent AaeFd4 and CpFd variants reversibly interconvert between similar valence-localized S = 1/2 and valence-delocalized S = 9/2 forms as a function of pH, with pKa values in the range 8.3-9.0, because of protonation of the coordinated serinate residue. However, freezing high-pH samples results in partial or full conversion from valence-delocalized S = 9/2 to valence-localized S = 1/2 [Fe2S2](+) clusters. MCD saturation magnetization data for valence-delocalized S = 9/2 [Fe2S2](+) centers facilitated determination of t...Continue Reading

References

Jan 1, 1993·Methods in Enzymology·A J ThomsonS J George
Jul 15, 1993·Biochemical and Biophysical Research Communications·J FujinagaJ Meyer
Aug 12, 1999·Biochemical and Biophysical Research Communications·C ChateletJ Meyer
Jul 8, 2000·Journal of Molecular Biology·A P YehD C Rees
Jun 15, 2005·Annual Review of Biochemistry·Deborah C JohnsonMichael K Johnson
Mar 26, 2008·Chemical Society Reviews·Edward I SolomonAbhishek Dey

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Citations

Feb 10, 2018·The Journal of Biological Chemistry·Huanyao GaoMichael K Johnson
Sep 19, 2015·Angewandte Chemie·Shenglai YaoMatthias Driess
Mar 19, 2019·Journal of the American Chemical Society·Kathrin StegmaierAntonio J Pierik

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