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Mössbauer Spectroscopy on Respiratory Complex I: The Iron—Sulfur Cluster Ensemble in the NADH-Reduced Enzyme Is Partially Oxidized.

Authors :
Bridges, Hannah R.
Bill, Eckhard
Hirst, Judy
Source :
Biochemistry. 1/10/2012, Vol. 51 Issue 1, p149-158. 10p.
Publication Year :
2012

Abstract

In nntochondria, complex I (NADH quinone oxidoreductase) couples electron transfer to proton translocation across an energy-transducing membrane. It contains a flavin mononucleotide to oxidize NADH, and an unusually long series of iron- sulfur (FeS) clusters that transfer the electrons to quinone. Understanding electron transfer in complex I requires spectroscopic and structural data to be combined to reveal the properties of individual clusters and of the ensemble. EPR studies on complex I from Bos taurus have established that five clusters (positions 1, 2, 3, 5, and 7 along the seven-duster chain extending from the flavin) are (at least partially) reduced by NADH. The other three dusters, positions 4 and 6 plus a cluster on the other side of the flavin, are not observed in EPR spectra from the NADH-reduced enzyrne~ they may remain oxidized, have unusual or coupled spin states, or their EPR signals may be too fast relaxing. Here, we use Mtissbauer spectroscopy on 57Fe-labeled complex I from the mitochondria of Yarrowia lipolytica to show that the cluster ensemble is only partially reduced in the NADH-reduced enzyme. The three EPR-silent dusters are oxidized, and only the terminal 4Fe cluster (position 7) is fully reduced. Together with the EPR analyses, our results reveal an alternating profile of higher and lower potential dusters between the two active sites in complex I; they are not consistent with the consensus picture of a set of isopotential dusters. The implications for intramolecular electron transfer along the extended chain of cthctors in complex I are discussed. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
00062960
Volume :
51
Issue :
1
Database :
Academic Search Index
Journal :
Biochemistry
Publication Type :
Academic Journal
Accession number :
70574321
Full Text :
https://doi.org/10.1021/bi201644x