Structure-function studies of iron-sulfur clusters and semiquinones in the NADH-Q oxidoreductase segment of the respiratory chain.
Our recent experimental data on iron-sulfur clusters and semiquinones in the complex I segment of the respiratory chain is presented, focusing on the Paracoccus (P.) denitrificans and bovine heart studies. The iron-sulfur cluster N2 has attracted the attention of investigators in the research field of complex I, since the mid-point redox potential of this cluster is the highest among all clusters in complex I, and is pH dependent (60 mV/pH). It is known that this cluster is located either in the NQO6 (NuoB in E. coli/PSST in bovine heart nomenclature) or in the NQO9 (NuoI/TYKY) subunit in the amphipathic domain of complex I. Our preliminary data indicate that the cluster N2 is located in the NuoB rather than the long-advocated NuoI subunit, and may have a unique ligand structure. We previously reported spin-spin interactions between cluster N2 and two distinct species of semiquinone (designated SQNf and SQNs) associated with complex I. A parallel intensity change was observed between the SQNf (g = 2.00) signal and the N2 split g parallel signal, further supporting our proposed interaction between SQNf and N2 spins.
Johnson Research Foundation, Philadelphia, PA 19104, USA. ohnishi@mail.med.upenn.edu
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Yano
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D000818:Animals; D016227:Benzoquinones / Q000737:chemistry* / Q000378:metabolism; D002417:Cattle; D004579:Electron Transport; D042967:Electron Transport Complex I; D006801:Humans; D007501:Iron / Q000737:chemistry* / Q000378:metabolism; D009206:Myocardium / Q000201:enzymology; D009247:NADH, NADPH Oxidoreductases / Q000737:chemistry* / Q000378:metabolism; D010231:Paracoccus denitrificans / Q000201:enzymology; D013329:Structure-Activity Relationship; D013455:Sulfur / Q000737:chemistry* / Q000378:metabolism
D016227:Benzoquinones; C025232:semiquinone radicals; D013455:Sulfur; D007501:Iron; D009247:NADH, NADPH Oxidoreductases; D042967:Electron Transport Complex I