Blog
About

  • Record: found
  • Abstract: found
  • Article: not found

Photoinduced electron transfer between the Rieske iron-sulfur protein and cytochrome c(1) in the Rhodobacter sphaeroides cytochrome bc(1) complex. Effects of pH, temperature, and driving force.

The Journal of Biological Chemistry

Thermodynamics, Cytochromes c1, Temperature, enzymology, Rhodobacter sphaeroides, Protein Conformation, Oxidation-Reduction, Mutation, Light, chemistry, Iron-Sulfur Proteins, Hydrogen-Ion Concentration, Electron Transport Complex III

Read this article at

ScienceOpenPublisherPubMed
Bookmark
      There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

      Abstract

      Electron transfer from the Rieske iron-sulfur protein to cytochrome c(1) (cyt c(1)) in the Rhodobacter sphaeroides cytochrome bc(1) complex was studied using a ruthenium dimer complex, Ru(2)D. Laser flash photolysis of a solution containing reduced cyt bc(1), Ru(2)D, and a sacrificial electron acceptor results in oxidation of cyt c(1) within 1 micros, followed by electron transfer from the iron-sulfur center (2Fe-2S) to cyt c(1) with a rate constant of 80,000 s(-1). Experiments were carried out to evaluate whether the reaction was rate-limited by true electron transfer, proton gating, or conformational gating. The temperature dependence of the reaction yielded an enthalpy of activation of +17.6 kJ/mol, which is consistent with either rate-limiting conformational gating or electron transfer. The rate constant was nearly independent of pH over the range pH 7 to 9.5 where the redox potential of 2Fe-2S decreases significantly due to deprotonation of His-161. The rate constant was also not greatly affected by the Rieske iron-sulfur protein mutations Y156W, S154A, or S154A/Y156F, which decrease the redox potential of 2Fe-2S by 62, 109, and 159 mV, respectively. It is concluded that the electron transfer reaction from 2Fe-2S to cyt c(1) is controlled by conformational gating.

      Related collections

      Author and article information

      Journal
      10.1074/jbc.M202594200
      12045199

      Comments

      Comment on this article