Inhibitor-enhanced electron transfer: Copper cytochrome c as a redox-inert probe of ternary complexes

Jian S. Zhou, Judith M. Nocek, Michael L. DeVan, Brian M. Hoffman*

*Corresponding author for this work

Research output: Contribution to journalArticle

56 Scopus citations

Abstract

Copper-substituted cytochrome c (CuCc) has been used as a structurally faithful, redox-inert inhibitor to probe the mechanism of electron transfer (ET) between Cc molecules and cytochrome c peroxidase (CcP). This inhibitor enhances photoinduced ET quenching of the triplet excited state of a zinc-substituted protein (ZnCcP or ZnCc) by its iron(III) partner (Fe3+Cc or Fe 3+CcP). These results show that CcP and Cc form a ternary complex in which one Cc molecule binds tightly at a surface domain of CcP having low ET reactivity, whereas the second Cc molecule binds weakly to the 1:1 complex at a second domain with markedly greater (∼103) reactivity. These results also rule out the possibility that Cc bound at the second domain cooperatively enhances ET to Cc at the first domain. The multiphasic kinetics observed for the photoproduced ET intermediate do not reflect electron self-exchange between two Cc molecules within the ternary complex.

Original languageEnglish (US)
Pages (from-to)204-207
Number of pages4
JournalScience
Volume269
Issue number5221
DOIs
StatePublished - 1995

ASJC Scopus subject areas

  • General

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