Resonance Raman characterization of archaeal and bacterial Rieske protein variants with modified hydrogen bond network around the [2Fe-2S] center

Toshio Iwasaki, Asako Kounosu, Derrick R.J. Kolling, Sangmoon Lhee, Antony R. Crofts, Sergei A. Dikanov, Takuro Uchiyama, Takashi Kumasaka, Hiroyuki Ishikawa, Miwa Kono, Takeo Imai, Akio Urushiyama

Research output: Contribution to journalArticlepeer-review

Abstract

The rate of quinol oxidation by cytochrome bc1 /b6f complex is in part associated with the redox potential (Em) 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 (St) and Tyr-Oη (as with the Y156W variant, which has a modified histidine Nε pKa,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-Sb/t stretching vibrations. This is not observed in the case of the hydrogen bond between the bridging sulfide ligand (Sb) and Ser-Oγ, which is weak and/or unfavorably oriented for extensive coupling with the Fe-Sb/t stretching vibrations. Published by Cold Spring Harbor Laboratory Press.

Original languageEnglish (US)
Pages (from-to)2019-2024
Number of pages6
JournalProtein Science
Volume15
Issue number8
DOIs
StatePublished - 2006

Keywords

  • Archaea
  • Cytochrome bc complex
  • Hydrogen bond
  • Resonance raman
  • Rhodobacter
  • Rieske protein
  • [2fe-2s] cluster

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology

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