Electron-transfer mechanisms through biological redox chains in multicenter enzymes

Lars J.C. Jeuken, Anne K. Jones, Stephen K. Chapman, Gary Cecchini, Fraser A. Armstrong

Research output: Contribution to journalArticlepeer-review

113 Scopus citations


A new approach for studying intramolecular electron transfer in multicenter enzymes is described. Two fumarate reductases, adsorbed on an electrode in a fully active state, have been studied using square-wave voltammetry as a kinetic method to probe the mechanism of the long-range electron transfer to and from the buried active site. Flavocytochrome c3 (Fcc3), the globular fumarate reductase from Shewanella frigidimarina, and the soluble subcomplex of the membrane-bound fumarate reductase of Escherichia coli (FrdAB) each contain an active site FAD that is redox-connected to the surface by a chain of hemes or Fe-S clusters, respectively. Using square-wave voltammetry with large amplitudes, we have measured the electron-transfer kinetics of the FAD cofactor as a function of overpotential. The results were modeled in terms of the FAD group receiving or donating electrons either via a direct mechanism or one involving hopping via the redox chain. The FrdAB kinetics could be described by both models, while the Fcc3 data could only be fit on the basis of a direct electron-transfer mechanism. This raises the likelihood that electron transfer can occur via a superexchange mechanism utilizing the heme groups to enhance electronic coupling. Finally, the FrdAB data show, in contrast to Fcc3, that the maximum ET rate at high overpotential is related to the turnover number for FrdAB measured previously so that electron transfer is the limiting step during catalysis.

Original languageEnglish (US)
Pages (from-to)5702-5713
Number of pages12
JournalJournal of the American Chemical Society
Issue number20
StatePublished - May 22 2002
Externally publishedYes

ASJC Scopus subject areas

  • Catalysis
  • General Chemistry
  • Biochemistry
  • Colloid and Surface Chemistry


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