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Cyanide inhibition of cytochrome c oxidase. A rapid-freeze e.p.r. investigation.

By P Jensen, M T Wilson, R Aasa and B G Malmström

Abstract

The inhibition of cytochrome c oxidase by cyanide, starting either with the resting or the pulsed enzyme, was studied by rapid-freeze quenching followed by quantitative e.p.r. It is found that a partial reduction of cytochrome oxidase by transfer of 2 electron equivalents from ferrocytochrome c to cytochrome a and CuA will induce a transition from a closed to an open enzyme conformation, rendering the cytochrome a3-CuB site accessible for cyanide binding, possibly as a bridging ligand. A heterogeneity in the enzyme is observed in that an e.p.r. signal from the cytochrome a3 3+-HCN complex is only found in 20% of the molecules, whereas the remaining cyanide-bound a3-CuB sites are e.p.r.-silent

Topics: Research Article
Year: 1984
DOI identifier: 10.1042/bj2240829
OAI identifier: oai:pubmedcentral.nih.gov:1144519
Provided by: PubMed Central
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