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A Cytochrome c Oxidase Model Catalyzes the Reduction of Oxygen to Water Under Rate-Limiting Electron Flux
We studied the selectivity of a functional model of cytochrome c oxidase's active site that mimics the coordination environment and relative locations of Fe_a3, Cu_B, and Tyr²⁴⁴. To control electron flux, we covalently attached this model and analogs lacking copper and phenol onto self-assembled monolayer–coated gold electrodes. When the electron transfer rate was made rate limiting, both copper and phenol were required to enhance selective reduction of oxygen to water. This finding supports the hypothesis that, during steady-state turnover, the primary role of these redox centers is to rapidly provide all the electrons needed to reduce oxygen by four electrons, thus preventing the release of toxic partially reduced oxygen species.: Science, 2007, 315, 5818, 1565-1568. DOI: 10.1126/science.1135844. Lead authors: Neal Devaraj, Richard Decreau.

Collmania 2006
Photos from the 2006 Collman Symposium are available here.

Interaction of nitric oxide with a functional model of cytochrome c oxidase. Cytochrome c oxidase (CcO) is a multimetallic enzyme that carries out the reduction of O2 to H2O and is essential to respiration, providing the energy that powers all aerobic organisms by generating heat and forming ATP. The oxygen-binding heme a3 should be subject to fatal inhibition by chemicals that could compete with O2 binding. Near the CcO active site is another enzyme, NO synthase, which produces the gaseous hormone NO. NO can strongly bind to heme a3, thus inhibiting respiration. However, this disaster does not occur. Using functional models for the CcO active site, we show how NO inhibition is avoided; in fact, it is found that NO can protect the respiratory enzyme from other inhibitors such as cyanide, a classic poison: Proc. Natl. Acad. Sci. U. S. A., 2008, 105(29), 9892-9896. Lead authors: AbhishekDey, Richard Decréau, Ying Yang

A Functional Nitric Oxide Reductase Model. The first functional heme/non-heme nitric oxide reductase (NOR) model is presented. The fully reduced diiron compound reacts with two equivalents of NO leading to the formation of one equivalent of N2O and the bis-ferric product. NO binds to both heme Fe and non-heme Fe complexes forming individual ferrous nitrosyl species. The mixed-valence species with an oxidized heme and a reduced non-heme FeB does not show NO reduction activity. These results are consistent with a so-called "trans" mechanism for the reduction of NO by NOR: Proc. Natl. Acad. Sci. U. S. A., 2008,105(41), 15660-15665.. Lead authors: Ying Yang, AbhishekDey, Richard Decréau

Last modified: October 29, 2008. Maintained by: Richard Decréau

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