反向电子转移完成了2,3,5-三四酸替代型核糖酶中的催化循环
Kanchana R Ravichandran, Ellen C Minnihan, Yifeng Wei
1Department of Chemistry and Chemical Biology, Harvard University , 12 Oxford Street, Cambridge, Massachusetts 02138, United States.
Journal of the American Chemical Society
|October 23, 2015
概括
这项研究揭示了大肠杆菌核糖核酸酶是如何通过激素途径将核酸二酸盐转化为脱氧核酸的. 引入一种改性氨酸 (F3Y) 允许观察关键的基质中间体,澄清了酶的催化循环.
科学领域:
- 生物化学
- 酵素学
- 激进化学
背景情况:
- 大肠杆菌Ia类核糖减少酶 (RNR) 是DNA合成的关键酶,由α2和β2子单元组成.
- 该酶通过涉及突和基的基因机制催化脱氧核化物 (dNDP) 的产生.
- 之前的研究受限于缓慢的形状变化,无法观察基质中间体.
研究的目的:
- 研究大肠杆菌类 Ia RNR 的基因传播途径和催化机制.
- 通过使用修改的β2子单元来克服观察过渡基中间体的局限性.
主要方法:
- 在β2子单元 (F3Y(•) -β2的位置上插入2,3,5-trifluorotyrosine以扰乱构造.
- 快速冷电磁共振 (EPR) 光谱和快速化学灭分析.
- 对F3Y(•) -β2,α2,CDP和ATP反应的动力分析.
主要成果:
- F3Y(•) -β2突变保持了催化活性,使得可以观察激素中间体.
- 在30s-1时观察到Y356和dCDP的产生,这表明有效的基因传播.
- 确定了限制速度的F3Y再氧化,并显示Y122 () 基被减少并重新氧化.
结论:
- 这项研究表明,在每个催化循环中,β2中的Y122 () 基会被减少并重新氧化.
- 提供了第一个直接证据,证明某个通路基在活性α2β2复合体中完成了催化循环.
- 阐明了蛋白质构成和基因中间体在大肠杆菌RNR功能中的作用.
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