Effects of Mutations in Aspartate 14 on the Spectroscopic Properties of the [Fe3S4]+,0 Clusters in Pyrococcus furiosus Ferredoxin
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- 作者：Randall E. Duderstadt ; Christopher R. Staples ; Phillip S. Brereton ; Michael W. W. Adams ; and Michael K. Johnson
- 刊名：Biochemistry
- 出版年：1999
- 出版时间：August 10, 1999
- 年：1999
- 卷：38
- 期：32
- 页码：10585 - 10593
- 全文大小：137K
- 年卷期：v.38,no.32(August 10, 1999)
- ISSN：1520-4995
文摘
The properties of [Fe3S4]+,0 clusters in wild-type and mutant forms of Pf Fd with Asp, Ser,Cys, Val, His, Asn, and Tyr residues occupying position 14, i.e., proximal to the three 
2-S atoms of thecluster, have been investigated by the combination of EPR, variable-temperature magnetic circular dichroism(VTMCD), and resonance Raman (RR) spectroscopies. Two distinct types of [Fe3S4] clusters are identifiedon the basis of the breadth of the S = 1/2 [Fe3S4]+ EPR resonances and the marked differences in theVTMCD spectra of the S = 2 [Fe3S4]0 clusters. On the basis of the available NMR data for [Fe3S4]+,0clusters in ferredoxins, the distinctive properties of these two types of [Fe3S4] clusters are interpreted interms of different locations of the more strongly coupled pair of irons in the oxidized clusters and thevalence-delocalized pair in the reduced clusters. Near-IR VTMCD measurements indicate the presence ofS = 9/2 valence-delocalized pairs in both types of [Fe3S4]0 clusters, and the spin-dependent delocalizationenergies associated with the Fe-Fe interactions were determined to be ~4300 cm-1 in both cases. Weconclude that the nature of the residue at position 14 in Pyrococcus furiosus ferredoxin is an importantdeterminant of the location of the reducible pair of irons in a [Fe3S4]+,0 cluster, and the redox propertiesof the wild-type and mutant ferredoxins are discussed in light of these new results.
2-S atoms of thecluster, have been investigated by the combination of EPR, variable-temperature magnetic circular dichroism(VTMCD), and resonance Raman (RR) spectroscopies. Two distinct types of [Fe3S4] clusters are identifiedon the basis of the breadth of the S = 1/2 [Fe3S4]+ EPR resonances and the marked differences in theVTMCD spectra of the S = 2 [Fe3S4]0 clusters. On the basis of the available NMR data for [Fe3S4]+,0clusters in ferredoxins, the distinctive properties of these two types of [Fe3S4] clusters are interpreted interms of different locations of the more strongly coupled pair of irons in the oxidized clusters and thevalence-delocalized pair in the reduced clusters. Near-IR VTMCD measurements indicate the presence ofS = 9/2 valence-delocalized pairs in both types of [Fe3S4]0 clusters, and the spin-dependent delocalizationenergies associated with the Fe-Fe interactions were determined to be ~4300 cm-1 in both cases. Weconclude that the nature of the residue at position 14 in Pyrococcus furiosus ferredoxin is an importantdeterminant of the location of the reducible pair of irons in a [Fe3S4]+,0 cluster, and the redox propertiesof the wild-type and mutant ferredoxins are discussed in light of these new results.