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Cytochrome c oxidase
Nitric
Oxide Reductase
Surface Modification
Metal–metal bonds
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Professor
Collman
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Department of Chemistry
Stanford University
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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 Fea3,
CuB, 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.
- Read Feature in Chemical
and Engineering News: An Electron Starved Enzyme
- Read Feature in Chemistry
World: Chemical Model Unlock’s
Key Enzyme’s Secrets
- 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
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