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

Protein Sci. 2006 Aug;15(8):2019-24. doi: 10.1110/ps.052035406.


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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Archaeal Proteins / chemistry*
  • Bacterial Proteins / chemistry*
  • Cysteine / chemistry
  • Electron Transport Complex III / chemistry*
  • Electron Transport Complex III / genetics
  • Hydrogen Bonding*
  • Iron-Sulfur Proteins / chemistry*
  • Iron-Sulfur Proteins / genetics
  • Mutagenesis, Site-Directed
  • Rhodobacter sphaeroides / enzymology*
  • Spectrum Analysis, Raman
  • Sulfolobus / enzymology*
  • Tyrosine / chemistry


  • Archaeal Proteins
  • Bacterial Proteins
  • Iron-Sulfur Proteins
  • Rieske iron-sulfur protein
  • Tyrosine
  • Electron Transport Complex III
  • Cysteine