Correlation of the cytochrome c₂ content of cyanobacterial Photosystem II with the EPR properties of the oxygen-evolving complex

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• 作者：Lakshmi ; K. V. ; Reifler ; Michael J. ; Chisholm ; Dexter A. ; Wang ; Jamie Y. ; Diner ; Bruce A. ; Brudvig ; Gary W.
• 关键词：cytochrome c 550 ; EPR spectroscopy ; metal ; affinity chromatography ; oxygen ; evolving complex ; Photosystem II ; Synechocystis PCC 6803
• 刊名：Photosynthesis Research
• 出版年：2002
• 出版时间：2002
• 年：2002
• 卷：72
• 期：2
• 页码：175-189
• 全文大小：562 KB

文摘

The Mn₄ cluster of PS II advances through a series of oxidation states (S states) that catalyze the breakdown of water to dioxygen in the oxygen-evolving complex. The present study describes the engineering and purification of highly active PS II complexes from mesophilic His-tagged Synechocystis PCC 6803 and purification of PS II core complexes from thermophilic wild-type Synechococcus lividus with high levels of the extrinsic polypeptide, cytochrome c₅₅₀. The g = 4.1 S₂ state EPR signal, previously not characterized in untreated cyanobacterial PS II, is detected in high yields in these PS II preparations. We present a complete characterization of the g = 4.1 state in cyanobacterial His-tagged Synechocystis PCC 6803 PS II and S. lividus PS II. Also presented are a determination of the stoichiometry of cytochrome c₅₅₀ bound to His-tagged Synechocystis PCC 6803 PS II and analytical ultracentrifugation results which indicate that cytochrome c₅₅₀ is a monomer in solution. The temperature-dependent multiline to g = 4.1 EPR signal conversion observed for the S₂ state in cyanobacterial PS II with high cytochrome c₅₅₀ content is very similar to that previously found for spinach PS II. In spinach PS II, the formation of the S₂ state g = 4.1 EPR signal has been found to correlate with the binding of the extrinsic 17 and 23 kDa polypeptides. The finding of a similar correlation in cyanobacterial PS II with the binding of cytochrome c₅₅₀ suggests a functional homology between cytochrome c₅₅₀ and the 17 and 23 kDa extrinsic proteins of spinach PS II.