Direct assignment of EPR spectra to structurally defined iron-sulfur clusters in complex I by double electron-electron resonance.

TitleDirect assignment of EPR spectra to structurally defined iron-sulfur clusters in complex I by double electron-electron resonance.
Publication TypeJournal Article
Year of Publication2010
AuthorsRoessler, MM, King, MS, Robinson, AJ, Armstrong, FA, Harmer, J, Hirst, J
JournalProc Natl Acad Sci U S A
Date Published2010 Feb 02
KeywordsAnimals, Bacterial Proteins, Cattle, Electron Spin Resonance Spectroscopy, Electron Transport, Electron Transport Complex I, Energy Transfer, Models, Molecular, Molecular Structure, Protein Structure, Tertiary, Thermus thermophilus

In oxidative phosphorylation, complex I (NADH:quinone oxidoreductase) couples electron transfer to proton translocation across an energy-transducing membrane. Complex I contains a flavin mononucleotide to oxidize NADH, and an unusually long series of iron-sulfur (FeS) clusters, in several subunits, to transfer the electrons to quinone. Understanding coupled electron transfer in complex I requires a detailed knowledge of the properties of individual clusters and of the cluster ensemble, and so it requires the correlation of spectroscopic and structural data: This has proved a challenging task. EPR studies on complex I from Bos taurus have established that EPR signals N1b, N2 and N3 arise, respectively, from the 2Fe cluster in the 75 kDa subunit, and from 4Fe clusters in the PSST and 51 kDa subunits (positions 2, 7, and 1 along the seven-cluster chain extending from the flavin). The other clusters have either evaded detection or definitive signal assignments have not been established. Here, we combine double electron-electron resonance (DEER) spectroscopy on B. taurus complex I with the structure of the hydrophilic domain of Thermus thermophilus complex I. By considering the magnetic moments of the clusters and the orientation selectivity of the DEER experiment explicitly, signal N4 is assigned to the first 4Fe cluster in the TYKY subunit (position 5), and N5 to the all-cysteine ligated 4Fe cluster in the 75 kDa subunit (position 3). The implications of our assignment for the mechanisms of electron transfer and energy transduction by complex I are discussed.

Alternate JournalProc. Natl. Acad. Sci. U.S.A.
Citation Key10.1073/pnas.0908050107
PubMed ID20133838
PubMed Central IDPMC2808219
Grant ListMC_U105663141 / / Medical Research Council / United Kingdom
MC_U105674181 / / Medical Research Council / United Kingdom