氨与光系统II氧气演变复合物的危险结合
Paul H Oyala1, Troy A Stich1, Richard J Debus2
1†Department of Chemistry, University of California, Davis, Davis, California 95616, United States.
Journal of the American Chemical Society
|June 18, 2015
概括
氨以终端NH3的形式与光系统II的团结,而不是作为桥梁. 这阐明了氧进化复合体中的基质结合和二氧化物形成机制.
科学领域:
- 生物化学 生物化学
- 光合作用研究研究光合作用.
- 结构生物学是结构生物学.
背景情况:
- 光系统II (PSII) 对于氧光合作用至关重要.
- 在PSII中氧化水的Mn4CaO5集群负责将水分解为氧气,质子和电子.
- 识别基质结合部位是理解氧气进化的关键.
研究的目的:
- 为了确定氨的精确结合点 (基质模拟物) 在PSII的氧进化复合体.
- 为了研究阿斯巴达酸-61在基质结合和水氧化中的作用.
- 为了阐明二氧化物形成的机制.
主要方法:
- PSII的高分辨率X射线晶体学.
- 脉冲电子偏磁共振 (EPR) 谱学. 脉冲电子偏磁共振 (EPR) 谱学.
- 位点定向的突变发生 (D1-D61A突变).
主要成果:
- X射线结构确定了Mn4CaO5星团附近的潜在基质结合点.
- D1蛋白的阿斯巴达-61与关键的水分子 (W1) 形成键,与Mn4A位点结合.
- 脉冲EPR光谱证实氨以NH3的形式与Mn4A位点结合,而不是作为桥接配体,在野生型和D1-D61A突变PSII中.
结论:
- 氨最终与Mn4A位点结合,挑战了以前关于桥梁相互作用的假设.
- 亚斯巴达-61和W1之间的键对于该位点的终端氨结合并不必不可少.
- 这一发现完善了我们对基质相互作用和PSII中水氧化的催化机制的理解.
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