The First State in the Catalytic Cycle of the Water-Oxidizing Enzyme: Identification of a Water-Derived μ-Hydroxo Bridge
| Autor: | Dimitrios A. Pantazis, Frank Neese, A. William Rutherford, Thomas Lohmiller, Vera Krewald, Nicholas Cox, Arezki Sedoud, Wolfgang Lubitz |
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| Rok vydání: | 2017 |
| Předmět: |
biology
010405 organic chemistry Chemistry Stereochemistry Substrate (chemistry) General Chemistry 010402 general chemistry 01 natural sciences Biochemistry Catalysis Cofactor 0104 chemical sciences law.invention Crystallography Colloid and Surface Chemistry Catalytic cycle law Oxidation state Oxidizing agent biology.protein Molecule Electron paramagnetic resonance |
| Zdroj: | Journal of the American Chemical Society. 139:14412-14424 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/jacs.7b05263 |
| Popis: | Nature’s water-splitting catalyst, an oxygen-bridged tetramanganese calcium (Mn4O5Ca) complex, sequentially activates two substrate water molecules generating molecular O2. Its reaction cycle is composed of five intermediate (Si) states, where the index i indicates the number of oxidizing equivalents stored by the cofactor. After formation of the S4 state, the product dioxygen is released and the cofactor returns to its lowest oxidation state, S0. Membrane-inlet mass spectrometry measurements suggest that at least one substrate is bound throughout the catalytic cycle, as the rate of 18O-labeled water incorporation into the product O2 is slow, on a millisecond to second time scale depending on the S state. Here, we demonstrate that the Mn4O5Ca complex poised in the S0 state contains an exchangeable hydroxo bridge. On the basis of a combination of magnetic multiresonance (EPR) spectroscopies, comparison to biochemical models and theoretical calculations we assign this bridge to O5, the same bridge identifie... |
| Databáze: | OpenAIRE |
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