Intermediates in Assembly by Photoactivation after Thermally Accelerated Disassembly of the Manganese Complex of Photosynthetic Water Oxidation
| Autor: | Holger Dau, Paola Loja, Michael Haumann, Marcos Barra, and Alexander Grundmeier, Roland Krivanek |
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| Rok vydání: | 2006 |
| Předmět: |
Manganese
Polarography Absorption spectroscopy Photosystem II biology Spectrum Analysis Inorganic chemistry Temperature Photosystem II Protein Complex Water chemistry.chemical_element Active site macromolecular substances Photochemistry Biochemistry Kinetics Membrane chemistry Spinacia oleracea Oxidation state biology.protein Photosynthesis Oxidation-Reduction Chlorophyll fluorescence |
| Zdroj: | Biochemistry. 45:14523-14532 |
| ISSN: | 1520-4995 0006-2960 |
| DOI: | 10.1021/bi061842z |
| Popis: | The Mn4Ca complex bound to photosystem II (PSII) is the active site of photosynthetic water oxidation. Its assembly involves binding and light-driven oxidation of manganese, a process denoted as photoactivation. The disassembly of the Mn complex is a thermally activated process involving distinct intermediates. Starting from intermediate states of the disassembly, which was initiated by a temperature jump to 47 degrees C, we photoactivated PSII membrane particles and monitored the activity recovery by O2 polarography and delayed chlorophyll fluorescence measurements. Oxidation state and structural features of the formed intermediates of the Mn complex were assayed by X-ray absorption spectroscopy at the Mn K-edge. The photoactivation time courses, which exhibit a lag phase characteristic of intermediate formation only when starting with the apo-PSII, suggest that within approximately 5 min of photoactivation of apo-PSII, a binuclear Mn complex is formed. It is proposed that a MnIII2(di-mu-oxo) complex is a key intermediate both in the disassembly and in the assembly reaction paths. |
| Databáze: | OpenAIRE |
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