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Mixed-valence cytochrome oxidase-formate complex. A steady-state intermediate.

T Brittain·C Greenwood·A Johnson
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Abstract

At neutral pH, formate binds to the haem a3 component of cytochrome c oxidase to give a complex that reacts differently from the non-liganded enzyme with reducing agents. Addition of sodium dithionite to the formate complex leads directly to the formation of the fully reduced species, whereas reduction with ascorbate/tetramethylenephenylene-diamine can lead to the production of a mixed-valence species. The stability of this mixed-valence form was studied, and the species appears to represent a 'steady-state' situation that is stable only in the presence of an excess of O2 and reducing equivalents. Characterization of the mixed-valence complex by electron paramagnetic resonance and magnetic circular dichroism reveals the presence of reduced low-spin haem a together with reduced detectable copper and high-spin ferric haem a3.

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Ascorbic AcidCircular DichroismElectron Spin Resonance SpectroscopyElectron Transport Complex IVFormatesOxidation-ReductionOxygenTetramethylphenylenediamineJournal Article

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T Brittain, C Greenwood, A Johnson. 1977-12-01. Mixed-valence cytochrome oxidase-formate complex. A steady-state intermediate.. https://doi.org/10.1042/bj1670531

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