title: Resonance Raman characterization of archaeal and bacterial Rieske protein variants with modified hydrogen bond network around the [2Fe-2S] center.
abstract: The rate of quinol oxidation by cytochrome bc(1)/b(6)f complex is in part associated with the redox potential (E(m)) of its Rieske [2Fe-2S] center, for which an approximate correlation with the number of hydrogen bonds to the cluster has been proposed. Here we report comparative resonance Raman (RR) characterization of bacterial and archaeal high-potential Rieske proteins and their site-directed variants with a modified hydrogen bond network around the cluster. Major differences among their RR spectra appear to be associated in part with the presence or absence of Tyr-156 (in the Rhodobacter sphaeroides numbering) near one of the Cys ligands to the cluster. Elimination of the hydrogen bond between the terminal cysteinyl sulfur ligand (S(t)) and Tyr-Oeta (as with the Y156W variant, which has a modified histidine N(epsilon) pK(a,ox)) induces a small structural bias of the geometry of the cluster and the surrounding protein in the normal coordinate system, and significantly affects some Fe-S(b/t) stretching vibrations. This is not observed in the case of the hydrogen bond between the bridging sulfide ligand (S(b)) and Ser-Ogamma, which is weak and/or unfavorably oriented for extensive coupling with the Fe-S(b/t) stretching vibrations.
authors.affiliation: Department of Biochemistry and Molecular Biology, Nippon Medical School, Sendagi, Tokyo, 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: Derrick R J
authors.initials: DR
authors.lastname: Kolling
authors.forename: Sangmoon
authors.initials: S
authors.lastname: Lhee
authors.forename: Antony R
authors.initials: AR
authors.lastname: Crofts
authors.forename: Sergei A
authors.initials: SA
authors.lastname: Dikanov
authors.forename: Takuro
authors.initials: T
authors.lastname: Uchiyama
authors.forename: Takashi
authors.initials: T
authors.lastname: Kumasaka
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ishikawa
authors.forename: Miwa
authors.initials: M
authors.lastname: Kono
authors.forename: Takeo
authors.initials: T
authors.lastname: Imai
authors.forename: Akio
authors.initials: A
authors.lastname: Urushiyama
mesh_terms: D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry*; D003545:Cysteine / Q000737:chemistry; D014450:Electron Transport Complex III / Q000737:chemistry* / Q000235:genetics; D006860:Hydrogen Bonding; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D012242:Rhodobacter sphaeroides / Q000201:enzymology*; D013059:Spectrum Analysis, Raman; D016944:Sulfolobus / Q000201:enzymology*; D014443:Tyrosine / Q000737:chemistry
chemical_list: D019843:Archaeal Proteins; D001426:Bacterial Proteins; D007506:Iron-Sulfur Proteins; C037989:Rieske iron-sulfur protein; D014443:Tyrosine; D014450:Electron Transport Complex III; D003545:Cysteine