title: Novel [2Fe-2S]-type redox center C in SdhC of archaeal respiratory complex II from Sulfolobus tokodaii strain 7.
abstract: The SdhC subunit of the archaeal respiratory complex II (succinate:quinone oxidoreductase) from Sulfolobus tokodaii strain 7 has a novel cysteine rich motif and is also related to archaeal and bacterial heterodisulfide reductase subunits. We overexpressed the sdhC gene heterologously in Escherichia coli and characterized the gene product in greater detail. Low temperature resonance Raman and x-ray absorption spectroscopic investigation collectively demonstrate the presence of a [2Fe-2S] cluster core with complete cysteinyl ligation (Center C) and an isolated zinc site in the recombinant SdhC. The [2Fe-2S]2+ cluster core is sensitive to dithionite, resulting in irreversible breakdown of the Fe-Fe interaction. EPR analysis confirmed that the novel Center C is an inherent redox center in the archaeal complex II, showing unique EPR signals in the succinate-reduced state. Distinct subunit and cofactor arrangements in the S. tokodaii respiratory complex II, as compared with those in mitochondrial and some mesophilic bacterial enzymes, indicate modular evolution of this ubiquitous electron entry site in the respiratory chains of aerobic organisms.
authors.affiliation: Department of Biochemistry and Molecular Biology, Nippon Medical School, Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan. tiwasaki@nms.ac.jp
authors.forename: Toshio
authors.initials: T
authors.lastname: Iwasaki
authors.forename: Asako
authors.initials: A
authors.lastname: Kounosu
authors.forename: Miho
authors.initials: M
authors.lastname: Aoshima
authors.forename: Daijiro
authors.initials: D
authors.lastname: Ohmori
authors.forename: Takeo
authors.initials: T
authors.lastname: Imai
authors.forename: Akio
authors.initials: A
authors.lastname: Urushiyama
authors.forename: Nathaniel J
authors.initials: NJ
authors.lastname: Cosper
authors.forename: Robert A
authors.initials: RA
authors.lastname: Scott
mesh_terms: D001105:Archaea / Q000737:chemistry; D019843:Archaeal Proteins; D001426:Bacterial Proteins; D004578:Electron Spin Resonance Spectroscopy; D004926:Escherichia coli / Q000378:metabolism; D005420:Flavoproteins / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D007506:Iron-Sulfur Proteins / Q000737:chemistry; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D010084:Oxidation-Reduction; D016133:Polymerase Chain Reaction; D021122:Protein Subunits; D011994:Recombinant Proteins / Q000737:chemistry; D013052:Spectrometry, X-Ray Emission; D013059:Spectrum Analysis, Raman; D013385:Succinate Dehydrogenase; D016944:Sulfolobus / Q000737:chemistry* / Q000378:metabolism; D013696:Temperature; D013816:Thermodynamics; D015032:Zinc / Q000737:chemistry
chemical_list: D019843:Archaeal Proteins; D001426:Bacterial Proteins; D005420:Flavoproteins; D007506:Iron-Sulfur Proteins; D008565:Membrane Proteins; D021122:Protein Subunits; D011994:Recombinant Proteins; C084271:SdhA protein, Bacteria; C108097:SdhD protein, archaeal; D007501:Iron; C108095:SDHB protein, human; D013385:Succinate Dehydrogenase; D015032:Zinc