AI Article Synopsis
- - Fully oxidized cytochrome c oxidase (CcO) can pump protons during enzymatic activity, but not when isolated and one-electron reduced due to structural differences.
- - The enzymes show different structural states: [Fe(3+)-OH(-)] when active versus [Fe(3+)-O(2)(2-)-Cu(2+)] when isolated, with ambiguity in the electron density hinting at the presence of Cl(-).
- - An anomalous dispersion analysis confirmed that Cl(-) is absent between the iron and copper sites, indicating that the peroxide structure interacts with cytochrome c without changing metal oxidation states, which is linked to the proton pumping mechanism.
Article Abstract
Fully oxidized cytochrome c oxidase (CcO) under enzymatic turnover is capable of pumping protons, while fully oxidized CcO as isolated is not able to do so upon one-electron reduction. The functional difference is expected to be a consequence of structural differences: [Fe(3+)-OH(-)] under enzymatic turnover versus [Fe(3+)-O(2)(2-)-Cu(2+)] for the as-isolated CcO. However, the electron density for O(2)(2-) is equally assignable to Cl(-). An anomalous dispersion analysis was performed in order to conclusively demonstrate the absence of Cl(-) between the Fe(3+) and Cu(2+). Thus, the peroxide moiety receives electron equivalents from cytochrome c without affecting the oxidation states of the metal sites. The metal-site reduction is coupled to the proton pump.
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| http://dx.doi.org/10.1107/S0907444911022803 | DOI Listing |
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