Plant Biochemistry, University of Lund, POB 7007, S-220 07, Lund, Sweden.
Photosynth Res. 1993 Sep;37(3):217-25. doi: 10.1007/BF00032825.
Photosystem II (PS II) particles isolated from spinach in the presence of 10 μM CuSO4 contained 1.2 copper/300 Chl that was resistant to EDTA. When CuSO4 was not added during the isolation, PS II particles contained variable amounts of copper resistant to EDTA (0.1-1.1 copper/300 Chl). No correlation was found between copper content and oxygen evolving capacity of the PS II particles. To identify the copper binding protein, we developed a fractionation procedure which included solubilisation of PS II particles followed by precipitation with polyethylene glycol. A 22-fold purification of copper with respect to protein was achieved for a 28 kDa protein. Partial amino acid sequence of a 13 kDa fragment, obtained after V8 (endo Glu-C) protease treatment, showed identity with CP 26 over a 14 amino acid stretch. EPR measurements on the purified protein suggest oxygen and/or nitrogen as ligands for copper but tend to exclude sulfur. We conclude that the 28 kDa apoprotein of CP 26 from spinach binds one copper per molecule of CP 26. A possible function for this copper protein in the xanthophyll cycle is discussed.
从含有 10 μM CuSO4 的菠菜中分离的光系统 II（PS II）颗粒含有 1.2 个铜/300 叶绿素，该铜对 EDTA 具有抗性。在分离过程中未添加 CuSO4 时，PS II 颗粒中含有可抵抗 EDTA 的铜（0.1-1.1 铜/300 叶绿素）。铜含量与 PS II 颗粒的产氧能力之间没有相关性。为了鉴定铜结合蛋白，我们开发了一种分级程序，包括 PS II 颗粒的溶解，然后用聚乙二醇沉淀。相对于蛋白质，铜的纯度提高了 22 倍，得到了 28 kDa 蛋白质。用 V8（内切 Glu-C）蛋白酶处理后获得的 13 kDa 片段的部分氨基酸序列在 14 个氨基酸片段上与 CP 26 具有同源性。对纯化蛋白的 EPR 测量表明，铜的配体为氧和/或氮，但可能排除了硫。我们得出结论，菠菜 CP 26 的 28 kDa 脱辅基蛋白每个 CP 26 分子结合一个铜。讨论了这种铜蛋白在叶黄素循环中的可能功能。
