Intermediates in Assembly by Photoactivation after Thermally Accelerated Disassembly of the Manganese Complex of Photosynthetic Water Oxidation
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- 作者：Marcos Barra ; Michael Haumann ; Paola Loja ; Roland Krivanek ; Alexander Grundmeier ; Holger Dau
- 刊名：Biochemistry
- 出版年：2006
- 出版时间：December 5, 2006
- 年：2006
- 卷：45
- 期：48
- 页码：14523 - 14532
- 全文大小：172K
- 年卷期：v.45,no.48(December 5, 2006)
- ISSN：1520-4995
文摘
The Mn4Ca complex bound to photosystem II (PSII) is the active site of photosynthetic wateroxidation. Its assembly involves binding and light-driven oxidation of manganese, a process denoted asphotoactivation. The disassembly of the Mn complex is a thermally activated process involving distinctintermediates. Starting from intermediate states of the disassembly, which was initiated by a temperaturejump to 47 
C, we photoactivated PSII membrane particles and monitored the activity recovery by O2polarography and delayed chlorophyll fluorescence measurements. Oxidation state and structural featuresof the formed intermediates of the Mn complex were assayed by X-ray absorption spectroscopy at theMn K-edge. The photoactivation time courses, which exhibit a lag phase characteristic of intermediateformation only when starting with the apo-PSII, suggest that within ~5 min of photoactivation of apo-PSII, a binuclear Mn complex is formed. It is proposed that a MnIII2(di-
-oxo) complex is a key intermediateboth in the disassembly and in the assembly reaction paths.
C, we photoactivated PSII membrane particles and monitored the activity recovery by O2polarography and delayed chlorophyll fluorescence measurements. Oxidation state and structural featuresof the formed intermediates of the Mn complex were assayed by X-ray absorption spectroscopy at theMn K-edge. The photoactivation time courses, which exhibit a lag phase characteristic of intermediateformation only when starting with the apo-PSII, suggest that within ~5 min of photoactivation of apo-PSII, a binuclear Mn complex is formed. It is proposed that a MnIII2(di--oxo) complex is a key intermediateboth in the disassembly and in the assembly reaction paths.